U.S. Military Action Against the Islamic State:
Answers to Frequently Asked Legal Questions
Michael John Garcia
Legislative Attorney
Jennifer K. Elsea
Legislative Attorney
September 9, 2014
Congressional Research Service
7-5700
www.crs.gov
R43720
U.S. Military Action Against the Islamic State: Answers to Legal FAQs
Summary
The capture of significant portions of Iraqi territory in June 2014 by the Islamic State of Iraq and
the Levant (ISIL or ISIS), which has subsequently begun formally referring to itself as the Islamic
State (IS), has prompted renewed U.S. military action in Iraq, along with the discussion of
possible military strikes against IS forces located in Syria. Between March 2003 and the end of
2011, the U.S. military forces had been deployed in Iraq first to remove the Saddam Hussein
regime from power and then to assist the nascent post-Saddam government in responding to
threats to the country’s stability. Following the expiration of the U.S.-Iraq Security Agreement at
the end of 2011, offensive U.S. military operations ceased and most U.S. forces were withdrawn.
In the wake of a successful offensive in northern and central Iraq by the Islamic State in June
2014, however, the Iraqi government requested assistance by the United States in responding to
IS forces, including through airstrikes. Shortly thereafter, the United States deployed military
personnel to collect intelligence and logistical information regarding IS activities, advise Iraqi
security forces, and provide additional security to U.S. personnel and facilities located in Iraq.
Beginning in August, President Obama authorized U.S. forces to begin limited airstrikes against
the Islamic State to stop further advances by the insurgent forces, protect U.S. military and non-
military personnel, and support certain humanitarian operations within Iraq. Continuing activities
by the Islamic State, including the group’s apparent responsibility for the execution of two U.S.
journalists, have led some policy makers to consider the possibility of expanding the scope of
U.S. military action against the Islamic State. Thus far, President Obama has cited his authority
under Article II of the U.S. Constitution as the legal basis for these actions, rather than any
authority conferred by Congress via statute. Legislative proposals have also been considered,
including H.Con.Res. 105, passed by the House in July, and provisions within the House-passed
version of the Department of Defense Appropriations Act, 2015 (H.R. 4870), which appear
intended to constrain the executive’s ability to engage in certain types of military action in Iraq or
Syria without congressional authorization. A public address by President Obama is scheduled for
September 10, 2014, during which he is expected to announce the expansion of offensive
operations against the Islamic State.
This report addresses select legal questions raised by the use of military force against IS.
Questions addressed in this report include potential sources (and limitations) of presidential
authority to use military force against the Islamic State without congressional authorization; the
potential relevance of the 2002 Authorization for Use of Military Force Against Iraq (2002 Iraq
AUMF; P.L. 107-243) and the 2001 Authorization for Use of Military Force (2001 AUMF; P.L.
107-40); the applicability of the United Nations Charter to ongoing U.S. military strikes in Iraq
and any prospective strikes against IS forces in Syria; and the constraints imposed by the War
Powers Resolution upon U.S. military action that has not been authorized by Congress. The
report will be updated as warranted by events.
Many of the legal issues discussed in this report concerning congressional oversight of U.S.
military action are addressed in greater detail in CRS Report R41989, Congressional Authority to
Limit Military Operations, by Jennifer K. Elsea, Michael John Garcia, and Thomas J. Nicola.
Further discussion regarding recent developments in Iraq and Syria can be found in CRS Report
RS21968, Iraq: Politics, Governance, and Human Rights, by Kenneth Katzman; CRS Report
R43612, Iraq Crisis and U.S. Policy, by Kenneth Katzman et al.; and CRS Report RL33487,
Armed Conflict in Syria: Overview and U.S. Response, coordinated by Christopher M. Blanchard.
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U.S. Military Action Against the Islamic State: Answers to Legal FAQs
Contents
Introduction ...................................................................................................................................... 1
Does the Use of Force Against the Islamic State Require Congressional Authorization? ............... 3
Does the 2002 Iraq AUMF Authorize Military Action against the Islamic State? ........................... 7
Does the 2001 AUMF Authorize Military Action against the Islamic State? .................................. 9
How Does the War Powers Resolution Apply to Military Action against the Islamic State? ........ 10
Compelling Termination of U.S. Military Action via Concurrent Resolution ......................... 12
Cessation of Unauthorized Hostilities within 60 Days ............................................................ 13
Is the U.S. Military Action against the Islamic State Permitted under the United Nations
Charter? ...................................................................................................................................... 16
Contacts
Author Contact Information........................................................................................................... 20
Congressional Research Service
U.S. Military Action Against the Islamic State: Answers to Legal FAQs
Introduction
The capture of significant portions of Iraqi territory in June 2014 by the Islamic State of Iraq and
the Levant (ISIL or ISIS), which has subsequently begun formally referring to itself as the Islamic
State (IS), has prompted significant military operations by U.S. forces in Iraq for the first time in
more than three years. Between March 2003 and the end of 2011, the U.S. military forces had
been deployed in Iraq first to remove the Saddam Hussein regime from power and then to assist
the nascent post-Saddam government in responding to threats to the country’s stability.1
Following the expiration of the U.S.-Iraq Security Agreement at the end of 2011, offensive U.S.
military operations in Iraq were terminated and most U.S. forces were withdrawn from the
country.
In the wake of the successful offensive in northern and central Iraq by IS forces in June 2014,
however, the Iraqi government requested U.S. assistance in responding to advancing IS forces,
including through airstrikes.2 Shortly thereafter, the United States deployed military personnel to
collect intelligence and logistical information regarding IS activities, advise Iraqi security forces,
and bolster protection for U.S. personnel and facilities within Iraq.3 In early August, President
Obama authorized U.S. forces to begin limited airstrikes against IS forces to stop further
advances and to protect U.S. military and non-military personnel, including those providing
humanitarian assistance to Iraqi civilians trapped by IS-led forces on the Sinjar Mountain.4 A
week later, President Obama authorized additional airstrikes to assist Iraqi forces in recapturing
the Mosul Dam from IS forces.5 U.S. airstrikes were subsequently authorized in support of an
operation to deliver humanitarian assistance to civilians located in the town of Amirli and to
prevent an IS offensive against the Haditha Dam in Anbar Province.6 Continuing activities by the
1 For further discussion, see CRS Report RS21968, Iraq: Politics, Governance, and Human Rights, by Kenneth
Katzman.
2 See Craig Whitlock, U.S. military leaders warn of difficulty of conducting airstrikes in Iraq, online version,
WASHINGTON POST, June 18, 2014 (including embedded video of Army Gen. Martin E. Dempsey, chairman of Joint
Chiefs of Staff, acknowledging formal request by Iraqi government during testimony before Senate Appropriations
Committee).
3 White House, Office of Press Secretary, Letter from the President—War Powers Resolution Letter regarding Iraq,
June 26, 2014 (text of letter submitted to notify Congress of additional U.S. military forces in Iraq to advise Iraqi
security forces and collect intelligence and logistical information), available at http://www.whitehouse.gov/the-press-
office/2014/06/26/letter-president-war-powers-resolution-letter-regarding-iraq; White House, Office of Press Secretary,
Letter from the President—War Powers Resolution Letter regarding Iraq, June 30, 2014 (letter notifying Congress of
increase in U.S. forces to protect U.S. personnel and facilities in Iraq, and acknowledging an earlier notification which
was submitted on June 16, 2014 concerning previous deployment of U.S. forces for such purposes), available at
http://www.whitehouse.gov/the-press-office/2014/06/30/letter-president-war-powers-resolution-letter-regarding-iraq.
4 White House, Office of Press Secretary, Letter from the President—War Powers Resolution Letter regarding Iraq,
Aug. 8, 2014, available at http://www.whitehouse.gov/the-press-office/2014/08/08/letter-president-war-powers-
resolution-regarding-iraq.
5 White House, Office of Press Secretary, Letter from the President—War Powers Resolution Letter regarding Iraq,
Aug. 30, 2014, available at http://www.whitehouse.gov/the-press-office/2014/08/17/letter-president-war-powers-
resolution-regarding-iraq.
6 White House, Office of Press Secretary, Letter from the President—War Powers Resolution Letter regarding Iraq,
Sept. 1, 2014, available at http://www.whitehouse.gov/the-press-office/2014/09/01/letter-president-war-powers-
resolution-regarding-iraq; Letter from the President—War Powers Resolution Letter regarding Iraq, Sept. 8, 2014,
available at http://www.whitehouse.gov/the-press-office/2014/09/08/letter-president-war-powers-resolution-regarding-
iraq.
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U.S. Military Action Against the Islamic State: Answers to Legal FAQs
Islamic State, including the group’s apparent responsibility for the execution of two U.S.
journalists, have led some policy makers to consider the possibility of expanding the scope of
U.S. military action against the group, including potentially targeting IS forces located in Syria. A
public address by President Obama is scheduled for September 10, 2014, during which he is
expected to announce the expansion of offensive operations against the Islamic State.7
Thus far, President Obama has cited his authority under Article II of the U.S. Constitution as the
legal basis for these actions, rather than any authority conferred by Congress via statute. Military
and humanitarian operations have been carried out with previously appropriated funds.
Specifically, all notifications submitted by the President to Congress in accordance with the
requirements of the War Powers Resolution have characterized the relevant military actions as
having been undertaken pursuant to the President’s constitutional authority “to conduct U.S.
foreign relations and as Commander in Chief and Chief Executive.”8 Legislative proposals have
been introduced, including H.Con.Res. 105, passed by the House in July, and provisions within
the House-passed version of the Department of Defense Appropriations Act, 2015 (H.R. 4870),
which appear intended to constrain the executive’s ability to engage in certain types of military
action in Iraq or Syria without congressional authorization.9
This report addresses select legal questions raised by the use of military force against the Islamic
State. Questions addressed in this report include potential sources (and limitations) of presidential
authority to use military force against the Islamic State without new congressional authorization;
the potential relevance of the 2002 Authorization for Use of Military Force Against Iraq (2002
Iraq AUMF; P.L. 107-243) and the 2001 Authorization for Use of Military Force (2001 AUMF;
P.L. 107-40); the applicability of the United Nations (U.N.) Charter to ongoing U.S. military
strikes in Iraq and any prospective strikes against IS forces in Syria; and the constraints imposed
by the War Powers Resolution upon U.S. military action that has not been authorized by
Congress. The report will be updated as warranted by events.
Many of the legal issues discussed in this report concerning congressional oversight of U.S.
military action are addressed in greater detail in CRS Report R41989, Congressional Authority to
Limit Military Operations, by Jennifer K. Elsea, Michael John Garcia, and Thomas J. Nicola. A
brief overview of statutes potentially relevant to ongoing U.S. military operations in Iraq can also
be found in CRS Legal Sidebar WSLG970, Is the 2002 Iraq AUMF Still Good Law? And Can the
President Use Force in Iraq Regardless?, by Michael John Garcia and Michael John Garcia, and
CRS Insight IN10106, Use of Force Considerations in Iraq, by Matthew C. Weed. Further
discussion regarding recent developments in Iraq and Syria can be found in CRS Report
RS21968, Iraq: Politics, Governance, and Human Rights, by Kenneth Katzman; CRS Report
R43612, Iraq Crisis and U.S. Policy, by Kenneth Katzman et al.; and CRS Report RL33487,
Armed Conflict in Syria: Overview and U.S. Response, coordinated by Christopher M. Blanchard.
7 Transcript of interview of President Obama, NBC News, Meet the Press, Sept. 7, 2014 (discussing planned public
address concerning U.S. operations against the Islamic State), available at http://www.nbcnews.com/meet-the-press/
meet-press-transcript-september-7-2014-n197866.
8 See supra footnotes 4-6 (collecting various War Powers Resolution notifications).
9 H.R. 4870, as passed by the House, contains provisions which bar appropriated funds from being used in
contravention of the War Powers Resolution, both generally and with respect to military action in Iraq and Syria. H.R.
4870, House-passed version, §§8113, 9013, and 10012. The version of H.R. 4870 reported by the Senate Committee on
Appropriations would retain the provision barring funds from being used in contravention of the War Powers
Resolution with respect to military action in Syria.
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Does the Use of Force Against the Islamic State
Require Congressional Authorization?
The executive branch has cited the President’s independent authority under Article II of the U.S.
Constitution as the legal basis for the military action taken against the Islamic State so far, rather
than any authority conferred by Congress via statute.10 Some observers and lawmakers have
questioned whether some or all of these actions are lawful without congressional authorization,
and some wonder whether or at what point further military action would require express
congressional approval.11 President Obama has signaled that the continuation or expansion of
U.S. operations may require more “resources,”12 a possible indication of a perceived need for
Congress to consider and adopt appropriations to fund continuing operations.
The Constitution divides authority between Congress and the President on matters of war and the
use of military force. Under Article I, Section 8, Congress has the power to declare war, tax and
spend for the common defense, provide for the army and navy, make rules regulating the Armed
Forces, and make rules concerning captures.13 Additionally, Congress has authority to make all
laws “necessary and proper” for carrying out not only its own powers under Article I, Section 8
but also all of the powers vested by the Constitution in the executive and judicial branches as
well.14
On the executive side, the Constitution vests the President with the “executive Power,”15 and
appoints him “Commander in Chief of the Army and Navy of the United States,”16 and bound to
“take Care that the Laws be faithfully executed.”17 He is also required by oath to “faithfully
execute the Office of President of the United States,” and, to the best of his “Ability, preserve,
protect and defend the Constitution of the United States.”18 Although not explicitly made plain by
the Constitution, he is also understood to be primarily responsible for carrying out the country’s
foreign affairs.19
10 See supra footnotes 4-6 (collecting various War Powers Resolution notifications).
11 In July, over 100 Members of Congress signed a letter to the President arguing that congressional authorization is
necessary for “offensive military operations abroad,” and that military force in Iraq should be pursuant to an act of
Congress. Rep. Barbara Lee, Letter to the President, Jul. 2, 2014, available at http://lee.house.gov/sites/lee.house.gov/
files/wysiwyg_uploaded/Final%20Lee-Rigell%20Iraq%20Letter-%20July%2016.pdf.
12 Transcript of interview of President Obama, supra footnote 7.
13 Under Article I, Section 8, Congress has the power “To lay and collect Taxes ... to ... pay the Debts and provide for
the common Defence,” “To raise and support Armies,” “To provide and maintain a Navy,” “To make Rules for the
Government and Regulation of the land and naval Forces,” and “To declare War, grant letters of Marque and Reprisal,
and make Rules concerning Captures on Land and Water,” as well as “To provide for calling forth the Militia to
execute the Laws of the Union, suppress Insurrections and repel Invasions” and “To provide for organizing, arming,
and disciplining, the Militia, and for governing such Part of them as may be employed in the Service of the United
States.”
14 U.S. CONST., Art, I, §8, cl. 18.
15 U.S. CONST., Art, II, §1, cl. 1.
16 Id., §2, cl.1.
17 Id., §3.
18 Id., §1, cl. 8.
19 United States v. Curtiss-Wright Export Corp., 299 U.S. 304. 319-320 (1936) (discussing “plenary and exclusive
power of the President as the sole organ of the federal government in the field of international relations”).
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The circumstances when the executive may order the use of force without congressional
authorization have been the subject of long-standing inter-branch and scholarly debate. The
executive has long asserted that the President has independent authority to conduct at least some
military operations in the absence of an authorizing act of Congress,20 including protecting U.S.
persons abroad21 (and possibly foreign nationals, as well),22 repelling attacks against the United
States or its military forces,23 or defending a “national interest” of the United States.24
In legislative enactments, however, Congress has characterized the President’s independent
constitutional authority to introduce U.S. forces into hostilities as being significantly more limited
in scope. Notably, the War Powers Resolution of 1973 declares Congress’s view that:
20 See, e.g., Dept. of Justice, Office of Legal Counsel, Presidential Power to Use the Armed Forces Abroad Without
Statutory Authorization, 4 Op. O.L.C. 185, 187 (1980) (“We believe that the substantive constitutional limits on the
exercise of these inherent powers [to use military force] by the President are, at any particular time, a function of
historical practice and the political relationship between the President and Congress. Our history is replete with
instances of presidential uses of military force abroad in the absence of prior congressional approval.”).
21 See, e.g., Dept. of Justice, Office of Legal Counsel (OLC), Presidential Powers Relating to the Situation in Iran, 4
Op. O.L.C. 115, 120 (1979) (recognizing such authority and claiming that the “power has been used conspicuously in
recent years in a variety of situations. These include: landing troops in the Dominican Republic to protect the lives of
citizens believed to be threatened by rebels (1965), the Danang sealift during the collapse of Vietnam defense (1975),
the evacuation of Phnom Penh (Cambodia, 1975), the evacuation of Saigon (1975), the Mayaguez incident (1975),
evacuation of civilians during the civil war in Lebanon (1976), and the dispatch of forces to aid American victims in
Guyana (1978).”); Presidential Power to Use the Armed Forces Abroad Without Statutory Authorization, supra
footnote 20, at 187 (characterizing presidential power as permitting the use of force both to protect U.S. persons and
retaliate against those causing them injury); Deployment of United States Armed Forces to Haiti, 28 Op. O.L.C. 1, 6
(2004) (arguing that presidential war powers permitted deployment of U.S. forces in Haiti to protect U.S. persons and
property located there, following the collapse of the ruling government, as the President “could reasonably conclude
that they would be in danger if the country were to descend into lawlessness”). For discussion of the possible limits on
such authority, including a discussion of the limited case law concerning presidential authority to use military force to
protect U.S. persons, see CRS Legal Sidebar WSLG974, When Can the President Use Military Force to Rescue or
Protect U.S. Persons Abroad?, by Michael John Garcia and Victoria Slatton.
22 Dept. of Justice, OLC, Authority to Use United States Military Forces in Somalia, 16 Op. O.L.C. 6, 11 (1992) (“Past
military interventions that extended to the protection of foreign nationals provide precedent for action to protect
endangered Somalians and other non-United States citizens.”).
23 Dept. of Justice, OLC, Legal Authorities Supporting the Activities of the National Security Agency Described by the
President, 32 Op. O.L.C. 1, 28-29 (2006) (“Among the President’s most basic constitutional duties is the duty to
protect the Nation from armed attack. The Constitution gives him all necessary authority to fulfill that responsibility.”).
Both the legislative and judicial branches have recognized that the President possesses independent constitutional
authority to authorize the use of force to defend the country against attack, but the scope of such authority may be the
subject of debate and disagreement. See Prize Cases, 67 U.S. (2 Bl.) 635, 668 (1863) (upholding lawfulness of Union
blockade of Southern ports instituted by President Lincoln in April 1861, at a time when Congress was not in session,
and “[The President] does not initiate war, but is bound to accept the challenge without waiting for any special
legislative authority.”); War Powers Resolution, P.L. 93-148 (1973), §2, codified at 50 U.S.C. §1541(c)(3)
(characterizing the President’s Commander-in-Chief authority as enabling him to introduce U.S. forces in hostilities in
the case of a “national emergency created by attack upon the United States, its territories or possessions, or its armed
forces.”).
24 Dept. of Justice, OLC, Authority to Use Military Force in Libya, 6-7 (2011), available at http://www.justice.gov/
sites/default/files/olc/opinions/2011/04/31/authority-military-use-in-libya_0.pdf. National interests that have been
claimed by the executive to support the use of force in the absence of congressional authorization have included, inter
alia, for purposes of protecting regional stability (including as a result of a humanitarian crisis), enforcing United
Nations Security Council mandates, and supporting U.S. personnel involved in U.N.-supported relief efforts. Id. (citing
prior assertions of national interests supporting U.S. military action relating to Somalia, Haiti, and Bosnia).
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The constitutional powers of the President as Commander-in-Chief to introduce United
States Armed Forces into hostilities, or into situations where imminent involvement in
hostilities is clearly indicated by the circumstances, are exercised only pursuant to
(1) a declaration of war,
(2) specific statutory authorization, or
(3) a national emergency created by attack upon the United States, its territories or
possessions, or its armed forces.25
Although U.S. courts have occasionally found the exercise of military power to be impermissible
when it is found to exceed or conflict with relevant statutory authority,26 there has been little
jurisprudence concerning the scope of presidential authority to order the use of force when
Congress has neither expressly authorized nor prohibited military action. A determination of the
permissibility of military action that has not been authorized by Congress may require
consideration of Congress’s will towards the President’s action and an assessment of how the
Constitution allocates the asserted power between Congress and the President. When the
allocation of power between the executive and legislative branches is unclear, Congress’s support
for, or “inertia, indifference, or quiescence” to executive action, may be relevant to an assessment
of the action’s constitutional validity.27
In Dames & Moore v. Regan, the Supreme Court assessed the legality of presidential actions
which fall within the “zone of twilight in which [the President] and Congress may have
concurrent authority, or in which its distribution is uncertain.”28 In such circumstances, the Court
indicated that the validity of the President’s action may depend on consideration of all
circumstances which shed light on the views of the legislative branch towards the action. In
Dames & Moore, the petitioners challenged an executive order by President Carter to establish
25 War Powers Resolution, P.L. 93-148 (1973), §2, codified at 50 U.S.C. §1541(c). The executive branch has
consistently disagreed with this characterization of the scope of its independent constitutional authority to commit U.S.
forces to hostilities.
26 See, e.g., Hamdan v. Rumsfeld, 548 U.S. 557 (2006) (striking down military tribunals established by presidential
order to try persons captured in conflict with Al Qaeda because the tribunals did not comply with relevant statutory
requirements);Youngstown Sheet and Tube Co. v. Sawyer, 343 U.S. 579 (1952) (striking down a presidential order
requiring the military to take possession of steel mills in order to keep up production for the Korean conflict); Ex Parte
Milligan, 71 U.S. (4 Wall.) 2 (1866) (giving effect to a statute suspending habeas corpus for prisoners of war rather
than a presidential order which proclaimed the privilege suspended for a broader category of persons); Little v.
Barreme, 6 U.S. (2 Cr.) 170 (1804) (finding seizure of vessel during limited hostilities with France could not be
justified by presidential order, as order exceeded parameters of statutory authorization). Conversely, there appears to be
no instance where a U.S. court has struck down a legislative enactment on the grounds that it impermissibly intruded
upon the President’s constitutional authority as Commander in Chief.
27 Youngstown, 343 U.S. at 637 (Jackson, J., concurring). Justice Jackson’s concurring opinion established a tripartite
analytical framework that is often used by reviewing courts to assess the propriety of presidential action:
When the President acts pursuant to an express or implied authorization of Congress, his powers
are at their maximum.... Congressional inertia, indifference or quiescence may ... invite, measures
of independent Presidential responsibility.... When the President takes measures incompatible with
the expressed or implied will of Congress, his power is at its lowest ebb, for then he can rely only
upon his own constitutional powers minus any constitutional powers of Congress over the matter.
Id. at 635-638.
28 Dames & Moore v. Regan, 453 U.S. 654, 668 (1981) (quoting Youngstown, 343 U.S. at 637 (Jackson, J.,
concurring)).
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regulations furthering compliance with the terms of a claim-settling executive agreement with
Iran. Congress had not expressly authorized these measures via statute. Nonetheless, the Court
found that Congress’s historical treatment of similar matters had evidenced intent to accord the
President broad discretion to act on the matter:
Although we have declined to conclude that [the relevant statute] directly authorizes the
President’s suspension of claims for the reasons noted, we cannot ignore the general tenor of
Congress’ legislation in this area in trying to determine whether the President is acting alone
or at least with the acceptance of Congress. As we have noted, Congress cannot anticipate
and legislate with regard to every possible action the President may find it necessary to take
or every possible situation in which he might act. Such failure of Congress specifically to
delegate authority does not, “especially ... in the areas of foreign policy and national
security,” imply “congressional disapproval” of action taken by the Executive. On the
contrary, the enactment of legislation closely related to the question of the President’s
authority in a particular case which evinces legislative intent to accord the President broad
discretion may be considered to “invite” “measures on independent presidential
responsibility.” At least this is so where there is no contrary indication of legislative intent
and when, as here, there is a history of congressional acquiescence in conduct of the sort
engaged in by the President.29
The Court “has been careful to note that past practice does not, by itself, create power.”30
However, in at least some instances, it appears that a history of congressional acquiescence to
long-standing presidential practice in a particular field “may be treated as a gloss on ‘Executive
Power’ vested in the President.”31
In the case of military affairs, the executive has argued that there has been a “historical pattern of
presidential initiative and congressional acquiescence” to the use of military force in certain
situations where statutory authorization has not been given.32 Accordingly, the executive may
claim that congressional inaction in this realm is entitled to a greater degree of legal significance
than would congressional acquiescence to executive action in another field.
The executive branch, while taking the view that not all military action requires congressional
authorization, has acknowledged that action of a certain intensity requires the approval of
Congress (at least when such action is not done to defend the country from attack, etc.). In a 2011
opinion from the Department of Justice’s Office of Legal Counsel concerning the legality of
military action in Libya, for example, it was alleged that:
[T]he historical practice of presidential military action without congressional approval
precludes any suggestion that Congress’s authority to declare war covers every military
engagement, however limited, that the President initiates. In our view, determining whether a
particular planned engagement constitutes a “war” for constitutional purposes instead
requires a fact-specific assessment of the “anticipated nature, scope, and duration” of the
29 Dames & Moore, 453 U.S. 678-679 (internal citations omitted).
30 Medellin v. Texas, 552 U.S. 491, 531-532 (2008) (internal citations omitted).
31 Dames & Moore, 453 U.S. at 686 (quoting Youngstown, 343 U.S. at 611 (Frankfurter, J., concurring)).
32 OLC Opinion on Use of Force without Congressional Authorization, supra footnote 20, at 187 (“We believe that the
substantive constitutional limits on the exercise of these inherent powers by the President are, at any particular time, a
function of historical practice and the political relationship between the President and Congress. Our history is replete
with instances of presidential uses of military force abroad in the absence of prior congressional approval.”). On several
occasions in the nation’s history, the President has ordered the use of military force without clear statutory
authorization.
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planned military operations. This standard generally will be satisfied only by prolonged and
substantial military engagements, typically involving exposure of U.S. military personnel to
significant risk over a substantial period.33
The executive’s characterization of its constitutional authority to act militarily in the absence of
congressional authorization, including whether congressional inaction constitutes “acquiescence”
to presidential assertions of independent authority, has been criticized by some observers and
Members of Congress.34 However, U.S. courts have not yet found the opportunity to consider the
validity of these claims, in part because challenges to military actions that have not been
unauthorized by Congress have typically been dismissed on procedural grounds without the
reviewing court reaching the merits of the litigants’ claims.35
Does the 2002 Iraq AUMF Authorize Military Action
against the Islamic State?36
As of the date of this report, the Obama Administration has not cited to the 2002 Iraq AUMF in
public statements concerning the legal basis for military action against IS. Indeed, shortly after
the deployment of U.S. military forces to Iraq to provide logistical and other support to Iraqi
security forces (but prior to the commencement of U.S. airstrikes against IS), the White House
reaffirmed its support for the repeal of the 2002 Iraq AUMF.37 Some have questioned whether the
2002 Iraq AUMF could be construed to provide statutory authorization for U.S. military action
against the Islamic State and other security threats presently located in Iraq.38
The 2002 Iraq AUMF was enacted in response to the perceived threat posed by the regime of
Saddam Hussein, and in particular the prospect that Iraq had or was acquiring weapons of mass
destruction. However, the operative clauses of the 2002 law do not specifically refer to the
33 OLC Opinion on Military Action against Libya, supra footnote 24, at 8.
34 See, e.g., Letter from Members to Congress on Military Action against the Islamic State, supra footnote 11 (stating
that the Constitution vests Congress with responsibility for authorizing the offense use of military force abroad); Curtis
A. Bradley & Trevor W. Morrison, Historical Gloss and Separation of Powers, 126 HARV. L. REV. 411, 466-467
(2012) (disputing certain executive claims concerning instances where Congress purportedly “acquiesced” to military
action taken without congressional authorization).
35 See generally CRS Report RL30352, War Powers Litigation Initiated by Members of Congress Since the Enactment
of the War Powers Resolution, by Michael John Garcia.
36 Portions of this discussion are taken from CRS Legal Sidebar WSLG970, Is the 2002 Iraq AUMF Still Good Law?
And Can the President Use Force in Iraq Regardless?, by Michael John Garcia and Michael John Garcia.
37 The White House, Letter from Susan E. Rice, Asst. to the President for National Security Affairs, to House Speaker
John A. Boehner, Jul. 25, 2014 (affirming Administration support for repeal of the 2002 Iraq AUMF, and stating that
the statute “is no longer used for any U.S. government activities”), available at http://armedservices.house.gov/
index.cfm/files/serve?File_id=D6A70EF0-E7ED-4A8B-B39B-9774CE10B7D3.
38 See, e.g, Alexander Bolton, Obama, Democrats Back in Iraq, THE HILL, June 18, 2014 (quoting a few lawmakers’
conflicting views concerning the applicability of the 2002 Iraq AUMF to military action against IS); Jack Goldsmith,
The 2002 Iraq AUMF Almost Certainly Authorizes the President to Use Force Today in Iraq (and Might Authorize the
Use of Force in Syria), LAWFARE BLOG, June 13, 2014 (arguing that plain text of 2002 Iraq AUMF may be reasonably
construed to permit military action to deal with the threat posed by an IS-destabilized Iraq), at
http://www.lawfareblog.com/2014/06/the-2002-iraq-aumf-almost-certainly-authorizes-the-president-to-use-force-
today-in-iraq-and-maybe-syria/; Jennifer Daskal, Ryan Goodman, & Steve Vladeck, The Premature Discussion of ISIS
and the 2001/2002 AUMFs, JUST SECURITY BLOG, June 17, 2014 (arguing that 2002 Iraq AUMF does not authorize
hostilities against IS, as purpose and design of the enactment concerned the Saddam Hussein regime).
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Hussein regime. Rather, the authorizing language of the 2002 Iraq AUMF permits the President to
use U.S. Armed Forces in certain specified instances, including to “defend the national security of
the United States against the continuing threat posed by Iraq.... ”39
Arguably, this language could be construed to cover any threat to U.S. national security interests
posed by a new crisis in Iraq, even after the removal of the Hussein regime and the establishment
of a new Iraqi government. Because the 2002 Iraq AUMF does not specifically define what
constitutes a “threat” to the “national security of the United States,” the statute arguably affords
the President a fair degree of discretion in assessing the meaning and application of those terms.
It might be possible, therefore, for some to argue that the IS insurgency, by threatening to impose
a new government in Iraq at odds with U.S. interests, makes Iraq once again a direct threat to
U.S. security.40 Accordingly, it might be argued that the operative language of the 2002 Iraq
AUMF confers authority on the President to use force to respond to this threat.
On the other hand, the context in which the 2002 Iraq AUMF was enacted, along with language
found in the act’s non-operative clauses which reference the “current Iraqi regime,”41 could be
cited in opposition to arguments that the 2002 Iraq AUMF authorizes U.S. military action over a
decade after Saddam Hussein’s regime had been deposed. Moreover, the withdrawal of most U.S.
forces from Iraq and the cessation of offensive military activities at the end of 2011 following the
termination of the U.S.-Iraq Security Agreement,42 along with subsequent statements by White
House officials that the 2002 Iraq AUMF is not used for current U.S. activities,43 provide grounds
for interpreting the enactment as not being relevant to U.S. military action against non-
government actors operating in Iraq in 2014.
If the 2002 Iraq AUMF is interpreted to cover the IS threat in Iraq, it may also become necessary
to address whether or to what extent the resolution authorizes military action against IS targets in
Syria. The answer to that question may be dependent on whether the conflict in Syria is deemed
to be part of the same armed conflict that is occurring in Iraq and whether this can be interpreted
to be a continuation of the original threat posed by Iraq. If the answer to both these questions is
yes, then the 2002 Iraq AUMF, which is not expressly limited to the territory of Iraq, may be read
impliedly to cover that part of the threat emanating from Syria. On the other hand, it might still be
argued that the threat IS operations in Syria pose to the Assad regime is not easily construed to be
a threat posed against U.S. national security “by Iraq,” and that the 2002 Iraq AUMF does not
confer statutory authorization of U.S. actions against IS forces located in Syria.
39 2002 Authorization for Use of Military Force Against Iraq, P.L. 107-243, §3(a)(1).
40 See President Barack Obama, Remarks by the President on the Situation in Iraq, White House, Office of the Press
Secretary, June 19, 2014 (claiming that “ISIL poses a threat to the Iraqi people, to the region, and to U.S. interests.”),
available at http://www.whitehouse.gov/the-press-office/2014/06/19/remarks-president-situation-iraq.
41 P.L. 107-243, preamble, cl. 8-9, 13, 17.
42 Withdrawal of United States Forces from Iraq and the Organization of Their Activities during Their Temporary
Presence in Iraq, 2008 U.S.T. LEXIS 115. Signed in Baghdad Nov. 17, 2008. Entered into force Jan. 1, 2009 and
effective until Jan. 1, 2012.
43 See, e.g., White House letter to House Speaker Boehner, supra footnote 37. See also President Barack Obama,
Remarks by the President and First Lady on the End of the War in Iraq, White House, Office of the Press Secretary,
Dec. 14, 2011 (stating that when U.S. troops completed their departure from Iraq at the end of the year, “America’s war
in Iraq will be over.”).
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Does the 2001 AUMF Authorize Military Action
against the Islamic State?
Although the 2001 AUMF has not been publicly cited by the Obama Administration as providing
statutory authorization for military action against the IS, it has been reported that the
Administration is reviewing the statute’s applicability.44 The 2001 AUMF has been the primary
domestic legal authority governing U.S. military action against Al Qaeda, the Taliban, and
associated forces. The application of the 2001 AUMF to the Islamic State would likely turn upon
the entity’s relationship with covered groups (and in particular, Al Qaeda), and whether this
relationship is sufficiently close for the group to be considered an “associated force.”
Following the terrorist attacks of September 11, 2001, Congress passed the 2001 AUMF, which
granted the President the authority:
to use all necessary and appropriate force against those nations, organizations, or persons he
determines planned, authorized, committed, or aided the terrorist attacks that occurred on
September 11, 2001, or harbored such organizations or persons, in order to prevent any
future acts of international terrorism against the United States by such nations, organizations
or persons.45
The AUMF clearly authorizes the President to use military force against entities responsible for
the terrorist attacks of 9/11, as well as certain entities that harbored them. Although neither
organization is expressly named by the AUMF, the statute has been construed by all three
branches of government to authorize military action against a number of entities: Al Qaeda (the
entity responsible for the 9/11 attacks); the Taliban (the entity which harbored them); and other
“associated forces” which have fought alongside these groups in hostilities against the United
States.46
The AUMF’s application to entities other than Al Qaeda and the Taliban has been the subject of
some debate, particularly regarding the nature and degree of support that would result in another
44 See Molly O’Toole, Obama, Iraq and the Coming War Powers Fight With Congress, DEFENSE ONE, Aug. 24, 2014
(quoting National Security Council spokeswoman Caitlin Hayden as stating that the Administration was “reviewing the
applicability of the 2001 AUMF to this situation”).
45 P.L. 107-40, §2(a).
46 See, e.g., National Defense Authorization Act for FY2012, P.L. 112-8, §1021(b) (construing the AUMF to permit the
detention of a “person who was a part of or substantially supported al-Qaeda, the Taliban, or associated forces that are
engaged in hostilities against the United States or its coalition partners, including any person who has committed a
belligerent act or has directly supported such hostilities in aid of such enemy forces”); In re Guantanamo Bay Detainee
Litigation, Respondents’ Memorandum Regarding the Government’s Detention Authority Relative to Detainees Held at
Guantanamo Bay, No. 08-0442, filed March 13, 2009 (D.D.C.) (brief filed by the executive in litigation concerning
Guantanamo detainees, claiming that the AUMF confers to the President “the authority to detain persons who were part
of, or substantially supported, Taliban or al-Qaida forces or associated forces that are engaged in hostilities against the
United States or its coalition partners, including any person who has committed a belligerent act, or has directly
supported hostilities, in aid of such enemy armed forces”), available at http://www.justice.gov/opa/documents/memo-
re-det-auth.pdf; Almerfedi v. Obama, 654 F.3d 1, 4 n.2 (D.C. Cir. 2011) (describing circuit court’s jurisprudence as
recognizing that under the AUMF, “the government may detain any individual engaged in hostilities ... against the
United States, who purposefully and materially supported hostilities against the United States or its coalition partners,
or who is part of the Taliban, al Qaeda, or associated forces”) (internal citations and quotations omitted).
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organization being deemed an “associated force.”47 The AUMF has not been construed by either
the executive or judicial branches as authorizing military action against an entity solely on
account of its participation in terrorism—indeed, entities that might sympathize with Al Qaeda’s
goals, but have no ties to the group, have been understood to fall outside the scope of the
AUMF.48 For their part, the officials within the executive branch have claimed that:
to be an “associated force,” a group must be both (1) an organized, armed group that has
entered the fight alongside al-Qa’ida or the Taliban and (2) a co-belligerent with al-Qa’ida or
the Taliban in hostilities against the United States or its coalition partners.49
Accordingly, an assessment of whether the 2001 AUMF confers statutory authorization for
military action against the Islamic State likely depends on the nature of the group’s relationship
with Al Qaeda or the Taliban, and in particular whether the group is properly considered an
“associated force.” Although antecedent entities to the Islamic State affiliated themselves with Al
Qaeda, the precise nature of the relationship between the Islamic State of Iraq and the
Levant/Islamic State and Al Qaeda leaders from 2006 onward is unclear. Current IS leaders have
reportedly stated that the Islamic State is not an offshoot of Al Qaeda.50
How Does the War Powers Resolution Apply to
Military Action against the Islamic State?
Enacted in 1973 over President Nixon’s veto, the War Powers Resolution (WPR)51 was an effort
by Congress to reassert its role in matters of war—a role that many Members believed had been
allowed to erode during the Korean and Vietnam conflicts. The WPR provides a mechanism by
which Congress may ostensibly force the President to withdraw U.S. forces from those hostilities
which had not been authorized by a declaration of war or specific statutory authorization. In more
than four decades since its enactment, however, the mechanisms to compel troop withdrawal have
never been successfully employed. Moreover, successive presidential administrations have
47 Litigation concerning the scope of persons covered by the AUMF has primarily arisen in the context of habeas
challenges brought by suspected enemy belligerents detained by the United States at the U.S. Naval Station in
Guantanamo Bay, Cuba or other locations. For a detailed discussion of such litigation, see CRS Report R41156,
Judicial Activity Concerning Enemy Combatant Detainees: Major Court Rulings, by Jennifer K. Elsea and Michael
John Garcia.
48 See, e.g., supra footnote 46 (noting legislative enactments, executive branch materials, and judicial rulings
addressing entities covered by the AUMF); Senate Foreign Relations Committee Hearing, Authorization For Use Of
Military Force After Iraq And Afghanistan, May 21, 2014, written testimony of Dept. of Defense General Counsel
Stephen W. Preston (“It is not the case in law or in practice that the concept of an ‘associated force’ is open-ended or
otherwise provides the Administration with unlimited flexibility to define the scope of the AUMF. A group that simply
embraces al-Qa’ida’s ideology is not an ‘associated force,’ nor is every group or individual that commits terrorist
acts.”), available at http://www.foreign.senate.gov/imo/media/doc/Preston_Testimony.pdf; Bensayah v. Obama, 610
F.3d 718, 725 (D.C. Cir. 2010) (“purely independent conduct of a freelancer” not enough for person to be considered
part of Al Qaeda, the Taliban, or an associated force); Hamlily v. Obama 616 F.Supp.2d 63, 75 n.17 (D.D.C., 2009)
(“’Associated forces’ do not include terrorist organizations who merely share an abstract philosophy or even a common
purpose with al Qaeda—there must be an actual association in the current conflict with al Qaeda or the Taliban.”).
49 Preston testimony, supra footnote 48.
50 For further discussion of the IS, including the group’s relationship with Al Qaeda, see CRS Report R43612, Iraq
Crisis and U.S. Policy, by Kenneth Katzman et al.
51 P.L. 93-148 (1973). For further background and explanation of the War Powers Resolution, see CRS Report
RL33532, War Powers Resolution: Presidential Compliance, by Richard F. Grimmett.
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viewed aspects of the WPR as unconstitutionally trenching upon the executive’s constitutional
authority in matters of war and foreign relations.52 Nonetheless, the WPR appears to constrain the
scope and duration of military action that may be taken against IS forces in the absence of
legislative authorization.
The WPR requires the President to consult with Congress “in every possible instance” prior to
introducing U.S. Armed Forces into actual or imminent hostilities.53 A report is required to be
submitted to Congress within 48 hours when, absent a declaration of war, U.S. Armed Forces are
introduced into “hostilities or ... situations where imminent involvement in hostilities is clearly
indicated by the circumstances.”54 Congressional notification is also required within 48 hours,
absent a declaration of war, when combat-equipped U.S. forces are deployed to a foreign nation,
or deployed in numbers which substantially enlarge the amount of combat-equipped U.S. forces
already stationed there.55
Section 5(b) of the WPR provides that after this report regarding the introduction of U.S. forces
into actual or imminent hostilities is submitted (or after such date that it was required to be
submitted), U.S. troops must thereafter be withdrawn within 60 days (or within 90 days in certain
circumstances),56 unless Congress authorizes continued involvement by passing a declaration of
war or some other specific authorization for continued U.S. involvement in hostilities.57
Moreover, Section 5(c) provides a means by which Congress may, at any time, compel the
withdrawal of U.S. forces from unauthorized hostilities occurring outside the United States by
means of a concurrent resolution.
52 See generally Dept. of Justice, Office of Legal Counsel, Authority of the President under Domestic and International
Law to Use Military Force against Iraq, 26 Op. O.L.C. 1, 39-45 (2002) (discussing presidential views and Dept. of
Justice opinions concerning the constitutionality of the War Powers Resolution). The Department of Justice’s Office of
Legal Counsel (OLC) has noted that while it had “has long questioned the constitutionality of the WPR, ...[it had] not
done so consistently.” Id. at 43 n.18. Although OLC opinions are not legally binding, they are generally adhered to
within the executive branch unless overruled by the President or the Attorney General.
53 50 U.S.C. §1542.
54 Id. at §1543(a)(1).
55 Id. at §1543(a)(2)-(3).
56 Id. at §1544. The sixty-day period may be extended by no more than thirty additional days if the President certifies in
writing to Congress that “unavoidable military necessity respecting the safety” of U.S. forces compels the continued
use of such forces in the course of bringing about their withdrawal. Id.
57 Id. See also 50 U.S.C. §1447(a)(1) (stating that authorization to introduce U.S. forces into hostilities shall not be
inferred “unless such provision specifically authorizes the introduction of United States Armed Forces”). Congress has
passed several measures authorizing the use of military force which describe themselves as constituting “specific
authorization” under the WPR. See e.g., P.L. 107-40 (2001) (the authorization to use force against entities responsible
for attacks of September 11, 2001 constituted specific authorization under the WPR); P.L. 107-243 (2002)
(authorization to use force against Iraq constituted specific authorization under the WPR); P.L. 102-1 (1991)
(authorization for first Persian Gulf conflict). The executive branch, however, has taken the position that the WPR does
not bind future Congresses from impliedly authorizing hostilities, and took the position that Congress had authorized
continuing hostilities against Yugoslavia via appropriations legislation, despite the fact that this legislation did not
describe itself as constituting specific authorization under the WPR. See Dept. of Justice, OLC, Authorization for
Continuing Hostilities in Kosovo, 24 Op. O.L.C. 327 (2000).
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Compelling Termination of U.S. Military Action via Concurrent
Resolution
On July 28, 2014, the House agreed to a concurrent resolution (H.Con.Res. 105) which provides
that “The President shall not deploy or maintain United States Armed Forces in a sustained
combat role in Iraq without specific statutory authorization for such use enacted after the date of
the adoption of this concurrent resolution.”58 The concurrent resolution, if agreed to by the
Senate, would appear to trigger the requirements of Section 5(c) of the WPR, and arguably
provide a mechanism by which Congress could compel the President to terminate any “sustained
combat role in Iraq” by U.S. forces. Existing jurisprudence concerning the legally binding nature
of concurrent resolutions, however, casts doubt on such a measure being interpreted to have legal
effect.
There appears to be a general consensus that the constitutional validity of Section 5(c) is doubtful
in the aftermath of the Supreme Court’s ruling in the 1983 case of INS v. Chadha.59 In Chadha,
the Court held that for a resolution to become a law, it must go through the bicameral and
presentment process in its entirety.60 Accordingly, concurrent or simple resolutions, which are not
presented to the President for his signature, could not be used as “legislative vetoes” against
executive action. Although the Chadha Court did not expressly find WPR Section 5(c) to be
unconstitutional, it was listed in Justice White’s dissent as one of nearly 200 legislative vetoes for
which the majority had sounded the “death knell,”61 and most commentators have agreed with
this assessment.62
It seems highly unlikely a concurrent resolution could legally compel the termination of U.S.
military operations, notwithstanding the requirements of Section 5(c) of the WPR. Nonetheless, a
concurrent resolution instructing the executive branch to terminate U.S. hostilities would seem to
counter any executive branch arguments that Congress had “acquiesced” to the President’s use of
military force.
58 The concurrent resolution does not attempt to define the nature or scope of U.S. military action which may constitute
a “sustained combat role in Iraq.”
59 462 U.S. 919 (1983).
60 Id. at 951.
61 Id. at 967, 1003 (White, J., dissenting).
62 See, e.g., Senate Foreign Relations Comm. Rep., Persian Gulf and the War Powers Resolution, S.REPT. NO. 106,
100th Cong., 1st Sess., at 6 (1987) (describing §5(c) as being “effectively nullified” by the Chadha decision); LOUIS
HENKIN, FOREIGN AFFAIRS AND THE U.S. CONSTITUTION 126-127 (2d. ed. 2002) (recognizing invalidation of §5(c) by
Chadha and describing arguments to the contrary as “plausible but not compelling”); FRANCIS D. WORMUTH AND
EDWIN B. FIRMAGE, TO CHAIN THE DOG OF WAR: THE WAR POWER OF CONGRESS IN HISTORY AND LAW 222 (2nd ed.
1989) (noting that the reasoning of Chadha “apparently invalidates section 5(c) of the War Powers Resolution”);
Ronald D. Rotunda, The War Powers Act in Perspective, 2 MICH. L. & POL’Y REV. 1, 8 (1997) (claiming that most
“scholars have concluded that... [§5(c)] is unconstitutional ever since INS v. Chadha). In contrast, some have argued
that neither a declaration of war nor a subsequent rescission of authorization to use force constitutes an “ordinary” act
of legislation falling under the requirements of the Presentment Clause. See Stephen L. Carter, The Constitutionality of
the War Powers Resolution, 70 VA. L. REV. 101, 130-132 (1984). The legitimacy of this argument is untested and
highly controversial, as Congress has always presented a declaration of war or authorization to use military force to the
President. Further, even assuming arguendo that a declaration of war does not need to be presented to the President, it
is not necessarily clear that legislation ending hostilities would also not require presentment. See HENKIN, supra at 127,
379; Carter, supra, at 130-132 (describing weaknesses of argument against presentment requirement); see also J.
Gregory Sidak, To Declare War, 41 DUKE L.J. 27, 84-85 (1991) (discussing historical and scholarly view that
presentment is necessary).
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Cessation of Unauthorized Hostilities within 60 Days
Section 5(b) of the WPR, which provides for the termination of U.S. military action within 60
days of the President submitting (or having been required to submit) a report of the introduction
of U.S. forces into actual or imminent hostilities, may constrain the executive’s ability to use
force against the Islamic State in the absence of further action by Congress. Although some legal
observers have raised constitutional concerns regarding Section 5(b),63 the weight of opinion,64
including possibly within the executive branch,65 appears to recognize the provision as a facially
permissible exercise of Congress’s constitutional authority over matters of war. Nonetheless, even
assuming that the provision is constitutionally valid, it does not necessarily act as a statutory
constraint to military action.
As an initial matter, Section 5(b) establishes a requirement for the withdrawal of U.S. troops 60
days after Armed Forces are introduced into actual or imminent hostilities without congressional
authorization, unless Congress subsequently enacts legislation providing authority for the use of
force or extends the deadline.66 Accordingly, if the 2002 Iraq AUMF or the 2001 AUMF are
construed as authorizing military action against the IS, Section 5(b) of the WPR would not
establish a deadline for the termination of U.S. military strikes against IS forces. For discussion of
the applicability of these statutes to military action against the IS, see supra at “Does the 2002
Iraq AUMF Authorize Military Action against the Islamic State?” and “Does the 2001 AUMF
Authorize Military Action against the Islamic State?”.
The executive branch has submitted numerous reports “consistent with the War Powers
Resolution” since June concerning U.S. military actions related to the IS. These reports have not
specified whether they are believed to satisfy the WPR’s requirements relating to the introduction
of U.S. forces into actual or imminent hostilities (which would trigger the 60-day timeline for the
63 See, e.g., Bradley Larschan, The War Powers Resolution: Conflicting Constitutional Powers, The War Powers, and
U.S. Foreign Policy, 16 DENVER J. INT’L L. & POL’Y 33, 44-45 (1987) (arguing that Section 5(b) of the WPR is
effectively “legislative veto” which is constitutionally impermissible post-Chadha, because it requires the President to
terminate the use of military force in the event that Congress fails to take any legislative action).
64 See, e.g., Carter, supra footnote 62, at 133 (charactering Section 5(b) as “surely constitutional, even after Chadha,”
and characterizing the provision as a sunset law rather than an unconstitutional legislative veto); HENKIN, supra
footnote 62, at 107-108 (taking the view that provisions of WPR other than Section 5(c) do not raise facial
constitutional objections); John Hart Ely, Suppose Congress Wanted a War Powers Act That Worked, 88 COLUM. L.
REV. 1379, 1392 (1988).
65 In a 1980 opinion, the Department of Justice’s OLC stated its view that “Congress may, as a general constitutional
matter, place a 60-day limit on the use of our armed forces as required by” the WPR. OLC Opinion on Use of Force
without Congressional Authorization, supra footnote 20, at 196 (1980). In an interview describing the Obama
Administration’s position that the WPR did not prohibit ongoing U.S. operations against Libya, Administration
officials acknowledged that the 1980 OLC Opinion remains in effect, and also claimed that the Administration’s
position that the U.S. military operation beyond 60 days was lawful was not premised on the view that the WPR is
unconstitutional. Charlie Savage and Mark Landler, White House Defends Continuing U.S. Role in Libya Operation,
N.Y. TIMES, June 16, 2011 (discussing interview with White House counsel Robert Bauer and State Department Legal
Adviser Harold Koh). See generally David J. Barron & Martin S. Lederman, The Commander in Chief at the Lowest
Ebb—A Constitutional History, 121 HARV. L. REV. 941, 1071 n.529 (2008) (discussing views of various presidential
administrations regarding the constitutionality of Section 5(b), and characterizing them as generally “complicated and
equivocal”).
66 The requirement in Section 5(b) does not apply in cases in which Congress “is physically unable to meet as a result
of an armed attack upon the United States.” 50 U.S.C. §1554. The 60-day deadline is automatically extended for thirty
days “if the President determines and certifies to the Congress in writing that unavoidable military necessity respecting
the safety of United States Armed Forces requires the continued use of such armed forces in the course of bringing
about a prompt removal of such forces.”
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termination of U.S. action under Section 5(b) of the WPR) or are intended to satisfy the
notification requirements concerning the deployment of combat-equipped U.S. forces into a
foreign country (which do not trigger the termination requirements). While the deployment of
U.S. forces to Iraq in June for purposes of protecting U.S. facilities and personnel located away
from active zones of combat could arguably be construed as not constituting the introduction of
U.S. forces into actual or imminent hostilities, this argument appears less persuasive with respect
to repeated U.S. airstrikes against the Islamic State that began in August.
It might be argued that each of the reports “consistent with” the WPR is intended to ensure the
activities described in each report trigger distinct 60-day termination requirements.67 Such an
interpretation, however, would seem to enable the executive to engage in unauthorized hostilities
against an enemy force for an indefinite period, so long as it promptly submitted reports to
Congress describing specific military actions that had been taken (e.g., the bombing of a
particular enemy facility; a battle with enemy forces at a particular location), each of which was
expected to last less than 60 days. This would appear to defeat the purpose of Section 5(b) of the
WPR, which was to assure the termination of unauthorized military action after a specified time
period even in the absence of action by Congress.
Moreover, disagreement may arise between the political branches regarding the scope of military
activities covered by Section 5(b). Such a disagreement occurred during U.S. operations in
support of the NATO-led mission against Muammar al Qadhafi’s regime in Libya. When U.S.
operations continued beyond the 60-day deadline for unauthorized hostilities established by the
WPR, some argued that Section 5(b) required their immediate termination unless authorization
was obtained from Congress. The Obama Administration did not challenge the constitutionality
of the WPR’s requirement that unauthorized hostilities be terminated within 60 days, but claimed
that this requirement did not apply to ongoing U.S. operations. The continued engagement in
manned and unmanned aerial attacks upon Libyan targets, in the Administration’s view, was
sufficiently limited so as not to constitute “hostilities” under the WPR, because they “do not
involve sustained fighting or active exchanges of fire with hostile forces, nor do they involve the
presence of U.S. ground troops.”68 The use of separate WPR reports for each anti-IS operation
may be intended to prevent the 60-day clock from starting at all, by suggesting that the scope and
duration of each operation is too limited to amount to “hostilities” within the meaning of the
WPR, even though the operations might seem more substantial in the aggregate.
The Obama Administration’s interpretation of the WPR’s application to military activity has been
criticized by some observers as overly constrained.69 Neither the express language of the WPR
nor the legislative history of the measure provide a precise indication as to the range of military
activities intended to be covered by the term “hostilities,” but the legislative history suggests that
Congress intended the act to apply to significant military engagements, including at least some
67 See Jack Goldmith, A New Tactic to Avoid War Powers Resolution Time Limits?, LAWFARE BLOG, Sept. 2, 2014, at
http://www.lawfareblog.com/2014/09/a-new-tactic-to-avoid-war-powers-resolution-time-limits/ (suggesting possible
rationales for the Administration’s decision to submit multiple WPR notifications to Congress).
68 Report to the House of Representatives on United States Activities in Libya, submitted June 15, 2011, at 25, available
at http://www.nytimes.com/interactive/2011/06/16/us/politics/20110616_POWERS_DOC.html?ref=politics.
69 See, e.g., David A. Fahrenthold &Felicia Sonmez, Congressmen Criticize Obama’s Stand on Libya, WASHINGTON
POST., June 16, 2011 (quoting House Speaker John Boehner and others expressing disagreement with the
Administration’s interpretation); Bruce Ackerman, Op-Ed, Legal Acrobatics, Illegal War, N.Y. TIMES, June 20, 2011,
available at http://www.nytimes.com/2011/06/21/opinion/21Ackerman.html.
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confrontations with belligerent forces that do not involve an exchange of fire.70 Moreover, at least
as a matter of international legal practice, repeated military strikes by one sovereign entity against
another entity may be deemed “hostilities,” even if such actions do not expose the attacking force
to serious threat of injury.71
Further, some have suggested that the Administration’s analysis too narrowly focuses on the
question of whether the U.S. operation can be construed as “hostilities” standing alone.72 Some
argue that in assessing whether U.S. forces are currently engaged in hostilities, it is appropriate to
consider the overarching military conflict, rather than simply the supporting role that U.S. forces
play within these operations.73 Under this interpretation, it would be appropriate to consider U.S.
actions in the broader context of the ongoing military action in Iraq, including military action not
only directly involving the United States, but also Iraqi security forces and the IS.74
Ultimately, however, it seems unlikely that the dispute will be definitively resolved by the courts.
Although there have been several instances where Members of Congress have brought suit
against the executive and argued that a particular military action contravenes the WPR or the
constitutional allocation of war powers (including a challenge to the Libyan action which was
dismissed on standing grounds),75 in all cases where final rulings have been issued, these
70 According to the House Report on the WPR:
[t]he word hostilities was substituted for the phrase armed conflict during the subcommittee drafting process because it
was considered to be somewhat broader in scope. In addition to a situation in which fighting actually has begun,
hostilities also encompasses a state of confrontation in which no shots have been fired but where there is a clear and
present danger of armed conflict. “Imminent hostilities” denotes a situation in which there is a clear potential either for
such a state of confrontation or for actual armed conflict.
H.R. Rep. 93-287 (1973), at 7. The legislative history suggests that the WPR was generally aimed at deterring “the
commitment of U.S. forces exclusively by the President ... without congressional approval or adequate consultation by
Congress.” Id.
71 See PIETRO VERRI, DICTIONARY OF THE INTERNATIONAL LAW OF ARMED CONFLICT 57 (International Comm. of the
Red Cross, ed., Edward Markee and Susan Mutti, trans.1992) (defining “hostilities” as “Acts of violence by a
belligerent against an enemy in order to put an end to his resistance and impose obedience.... ”).
72 See Jack Goldsmith, Problems with the Obama Administration’s War Powers Resolution Theory, LAWFARE BLOG,
June 16, 2011, at http://www.lawfareblog.com/2011/06/problems-with-the-obama-administration%E2%80%99s-war-
powers-resolution-theory-2/.
73 When authorizing Member States to prevent the Libyan government from attacking civilians, the U.N. Security
Council appeared to view such attacks as occurring within the context of an armed conflict between the Libyan
government and portions of the populace. See United Nations Security Council Res. 1973, at Preamble, cl. 3
(“Reiterating the responsibility of the Libyan authorities to protect the Libyan population and reaffirming that parties to
armed conflicts bear the primary responsibility to take all feasible steps to ensure the protection of civilians”).
Arguably, military action taken by coalition forces to protect Libyan civilians could be characterized as being a part of
this conflict.
74 Section 8(c) of the WPR indicates that references to the “introduction of U.S. Armed Forces” were intended to cover
situations where U.S. personnel, though perhaps not directly participating in combat operations themselves, “command,
coordinate, participate in the movement of, or accompany the regular or irregular military forces of any foreign country
or government when such military forces are engaged, or there exists an imminent threat that such forces will become
engaged, in hostilities.” 50 U.S.C. §1547(c). Arguably, this provision could be construed to support arguments that,
when examining whether U.S. forces are involved in “hostilities,” it is appropriate to look also to the operations of the
military forces that they assist. On the other hand, the Obama Administration has taken the position that this
definitional provision is not dispositive, as Section 8(c) “is textually linked (through the term ‘introduction of United
States Armed Forces’) not to the ‘hostilities’ language ... that triggers the automatic pullout provision in section 5(b),
but rather, to a different clause later down in that section that triggers a reporting requirement.” Senate Foreign
Relations Committee, Libya and War Powers, 112th Cong., 1st. Sess. (2011) (written testimony of State Department
Legal Adviser Harold Koh), available at http://www.state.gov/s/l/releases/remarks/167250.htm.
75 Kucinich v. Obama, 821 F. Supp. 2d 110 (D.D.C. 2011).
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challenges have been dismissed without the reviewing court reaching the underlying merits of the
litigants’ claims. The courts have variously relied on the political question doctrine, the
equitable/remedial discretion doctrine, ripeness, mootness, and congressional standing concerns
as grounds for dismissal.76 The courts have made clear, however, that while formidable, none of
the aforementioned procedural barriers constitutes an insurmountable obstacle to resolving the
statutory or constitutional issues concerning war powers. All of the opinions to date indicate that
the barrier to the exercise of jurisdiction stems from the posture of the cases, not some
institutional shortcoming. Absent such an irreconcilable conflict,77 however, many believe it is
unlikely that the courts will venture into this politically and constitutionally charged thicket.
Is the U.S. Military Action against the Islamic State
Permitted under the United Nations Charter?
As of the date of this report, U.S. military strikes against the Islamic State have occurred within
the territory of Iraq, and have been undertaken with the consent of the Iraqi government.
However, IS fighters “have used Syria both as a staging ground for attacks in Iraq and as a
parallel theater of operations,”78 leading some U.S. policy makers to consider the possibility of
attacking IS personnel and assets within Syria, as well.79 Syrian officials have stated, however,
that they would perceive military attacks by the United States or other outside forces as “act[s] of
aggression” if they were not undertaken with the cooperation and consent of the Syrian
government.80 In general, international law prohibits one state from acting militarily within the
76 See CRS Report RL30352, War Powers Litigation Initiated by Members of Congress Since the Enactment of the War
Powers Resolution, by Michael John Garcia (discussing various challenges brought by Members of Congress to
executive action which purportedly contravenes the War Powers Resolution). Lawsuits brought by private parties
alleging that presidential action has violated the WPR have also proven unsuccessful. See, e.g., Whitney v. Obama, 845
F. Supp. 2d 136 (D.D.C. 2012) (rejecting on mootness grounds a challenge by private parties alleging that U.S.
operations in Libya violated the WPR).
77 See CRS Report RL30352, War Powers Litigation Initiated by Members of Congress Since the Enactment of the War
Powers Resolution, by Michael John Garcia. See also Crockett v. Reagan, 558 F. Supp. 893, 899 (D.D.C. 1982)
(dismissing on political question grounds a challenge by several Members of Congress which claimed that the
executive’s military assistance to the government of El Salvador violated the WPR and constitutional allocation of war
powers, but suggesting that “were Congress to pass a resolution to the effect that a report was required under the WPR,
or to the effect that the forces should be withdrawn, and the President disregarded it, a constitutional impasse
appropriate for judicial resolution would be presented”), aff'd per curiam, 720 F.2d 1355, 1357 (D.C. Cir. 1983), cert.
denied, 467 U.S. 1251 (1984); Sanchez-Espinoza v. Reagan, 770 F.2d 202, 210-211 (D.C. Cir. 1985) (Ginsburg, Ruth
Bader, J., concurring) (agreeing on ripeness grounds with the dismissal of suit filed by several Members of Congress
which challenged the Reagan Administration’s provision of assistance to Nicaraguan Contra rebels, and emphasizing
that political branches had not as yet reached “a constitutional impasse” requiring judicial resolution).
78 CRS Report R43612, Iraq Crisis and U.S. Policy, by Kenneth Katzman et al., supra footnote 50, at 12 (quoting
version of report updated Aug.8, 2014).
79 In late August, President Obama approved the aerial surveillance of IS operations within Syria, reportedly as a
precursor to potential U.S. military attacks against IS fighters and assets located there. See Mark Landler & Helene
Cooper, Obama Authorizes Air Surveillance of ISIS in Syria, N.Y. TIMES, Aug. 25, 2014, available at
http://www.nytimes.com/2014/08/26/world/middleeast/obama-syria-ISIS.html.
80 See Liz Sly, Syria Warns against U.S. Strikes on Islamic State on Its Soil, WASHINGTON POST, Aug. 25, 2014
(quoting Syrian Foreign Minister Walid al-Moualem), available at http://www.washingtonpost.com/world/middle_east/
syria-warns-against-strikes-on-islamic-state-on-its-soil/2014/08/25/6fe98b38-2c5d-11e4-994d-
202962a9150c_story.html.
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territory of another without its consent. A few exceptions to this prohibition exist, most of which
are premised upon a nation’s inherent right to self-defense.81
Prior to World War II, states were recognized as having a sovereign right to use military force
against other states to vindicate any number of wrongs. In drafting the United Nations (U.N.)
Charter, member states sought to reduce the incidence of war by curtailing the rights of states to
use force against one another. Article 2(4) of the U.N. Charter generally prohibits member states
from using or threatening to use force “against the territorial integrity or political independence of
any state.”82
In the absence of authorization from the U.N. Security Council, the sole exception to this
prohibition that is expressly recognized by the U.N. Charter concerns the use of force by Member
States acting in collective or individual self-defense. Specifically, Article 51 preserves the
“inherent right of individual or collective self-defence if an armed attack occurs against a
Member of the United Nations, until the Security Council has taken measures necessary to
maintain international peace and security.”83 Read literally, Article 51’s articulation of the right
seems to preclude a state’s use of force until after an armed attack has already commenced and
not merely on the threat of any use of force,84 but some authorities regard the right as
encompassing the previously existing inherent right of self-defense under customary international
81 Some nations and outside observers have argued that humanitarian interventions (e.g., to deter human rights
violations or war crimes) may be permissible as well, even without U.N. Security Council approval and
notwithstanding the lack of clear recognition of such action in the U.N. Charter. See e.g., United Kingdom
Government, Chemical Weapon Use by Syrian Regime: UK Government Legal Position, Aug. 29, 2013 (proposing
criteria for when military force against a foreign state could be justified under the doctrine of humanitarian
intervention), available at https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/235098/
Chemical-weapon-use-by-Syrian-regime-UK-government-legal-position.pdf. Some proponents of legal recognition of
humanitarian intervention, even in the absence of U.N. Security Council authorization, point to the NATO-led military
action against Kosovo in 1999. Others, however, dispute the notion that the Kosovo action was purported by most
NATO parties to be legally justified pursuant to the doctrine of humanitarian intervention, and also note that relatively
few countries have taken the view that international law permits the use of force against another country solely on the
basis of humanitarian concerns. See Dapo Akande, The Legality of Military Action in Syria: Humanitarian Intervention
and Responsibility to Protect, BLOG OF THE EUROPEAN JOURNAL OF INTERNATIONAL LAW, Aug. 28, 2013, at
http://www.ejiltalk.org/humanitarian-intervention-responsibility-to-protect-and-the-legality-of-military-action-in-syria/
(discussing state recognition and non-recognition of the humanitarian intervention doctrine, and noting that in litigation
before the International Court of Justice only two NATO parties explicitly relied on the doctrine of humanitarian
intervention as legal justification for the Kosovo action). For its part, it does not appear that the executive branch of the
United States has ever taken the official view that international law permits military intervention on the basis of
humanitarian concerns alone.
82 UNITED NATIONS CHARTER, art. 2(3). The use of force is further precluded “in any other manner inconsistent with the
Purposes of the United Nations.” Id.
83 “Armed attack” is not defined by the U.N. Charter. The International Court of Justice has suggested that “armed
attack” is limited to attacks of sufficient intensity launched by or under the direction of a state. See e.g., Military and
Paramilitary Activities in and against Nicaragua (Nicar, v. U.S.), 1986 I.C.J. 14 (June 27); Oil Platforms (Iran v. U.S.),
42 I.L.M. 1334 (November 6, 2003); Armed Activities on the Territory of the Congo (Dem. Rep. Congo v. Uganda),
2005 I.C.J. 116, ¶ 147 (Dec. 19); Legal Consequences of the Construction of a Wall in the Occupied Palestinian
Territory, Advisory Opinion, 2004 I.C.J. 136, 215 (July 9). However, the UN Security Council recognized that the 9/11
attacks gave rise to a right to self defense. UN Sec. Council Res. 1368, S/RES/1368 (12 September 2001). Recent state
practice seems to confirm that attacks by non-state actors can amount to an armed attack and may give rise to a right of
self defense. See Michael Schmitt, Responding to Transnational Terrorism Under the Jus Ad Bellum, 56 Naval L. Rev.
1, 8 (2008) (positing that the international response to 9/11 demonstrates the acceptability of military force in response
to violent acts by non-state actors with no connection to any state, which until that time remained the province of law
enforcement).
84 YORAM DINSTEIN, WAR, AGGRESSION AND SELF-DEFENCE 166-68 (3d ed. 2001).
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law,85 which many likewise regard as including a right to preemptive (or “anticipatory”) self-
defense in the event of an imminent attack.86
If the state on whose territory force is to be used gives its consent, there is no violation of Article
2(4) of the UN Charter and therefore no need to invoke a theory of self-defense. Accordingly,
ongoing U.S. military actions against IS forces in Iraq do not raise concerns of a violation of
Iraq’s territorial integrity, as these actions have been undertaken with the consent of the Iraqi
government. On the other hand, military action by the United States against IS forces in Syria,
absent the consent of the Syrian government (or authorization by the U.N. Security Council),
would appear to conflict with the requirements of the U.N. Charter unless it could be justified as
an exercise of the inherent right of individual or collective self-defense that would be permissible
under Article 51.
The classic formulation of the right to use force in self-defense on the territory of a foreign state
was set forth by U.S. Secretary of State Daniel Webster in connection with the famous Caroline
incident. In 1837 British troops attacked a private American ship, the Caroline, while it was
moored for the night on the New York side of the Niagara River, asserting that the ship was being
used to provide supplies to insurrectionists against British rule in Canada who were based on an
island on the Canadian side of the river. The United States protested this “extraordinary outrage”
and demanded an apology and reparations. In the course of the ensuing diplomatic exchanges
with the British Government, Secretary of State Daniel Webster asserted that an intrusion into the
territory of another state can be justified as an act of self-defense only in those “cases in which
the necessity of that self-defence is instant, overwhelming, and leaving no choice of means and
no moment for deliberation.”87 Moreover, he wrote that even if justified, the use of defensive
force must be proportional to the threat, “since the act, justified by the necessity of self-defence,
must be limited by that necessity, and kept clearly within it.”88
The three conditions of necessity, proportionality, and immediacy (or imminence) are widely
regarded as establishing the grounds for invoking the right to resort to force extraterritorially.89
The application of these conditions to military action by the United States against IS forces in
Syria may depend, in part, upon whether such action is characterized as an act of self-defense by
85 THE CHARTER OF THE UNITED NATIONS: A COMMENTARY 666-67 (Bruno Simma, ed.,1994) (hereinafter “UN
COMMENTARY”) (describing the “prevailing view” as holding that Article 51 is a limitation on the customary right of
self-defense, while noting that an opposing view considers that Article 51 preserves a customary right of self-defense
that is not limited to cases of armed attack, but may be invoked against lesser threats); DINSTEIN, supra footnote 84, at
167-68 (noting, but disagreeing with a “strong school of thought maintaining that Article 51 only highlights one form
of self-defence ... ,[but] does not negate other patterns of legitimate action in self-defence”).
86 UN Commentary, supra footnote 85, at 675 (describing lack of consensus in international legal doctrine with respect
to the point at which self-defense measures may be taken); DINSTEIN, supra footnote 84, at 165-66 (assessing that the
majority of commentators regard self-defense under customary international law as encompassing a right to
anticipatory self-defense, but arguing that the right of self-defense under the UN Charter is more restricted); ANTONIO
CASSESSE, INTERNATIONAL LAW 307-11 (2001) (describing U.S. position on self-defense as broader than that which
appears to be generally accepted among states).
87 Letter from Secretary of State Daniel Webster to Lord Ashburton of August 6, 1842, set forth in JOHN BASSETT
MOORE, 2 A DIGEST OF INTERNATIONAL LAW 412 (1906).
88 Letter from Mr. Webster to Mr. Fox of April 24, 1841, 29 BRITISH AND FOREIGN STATE PAPERS 1129, 1138 (1857),
quoted in LORI DAMROSCH, INTERNATIONAL LAW: CASES AND MATERIALS 923 (2001).
89 DINSTEIN, supra footnote 84, at 219 (noting that the Webster correspondence has come to be “looked upon as
transcending the specific legal contours of extra-territorial law enforcement” to influence the entire field of self
defense).
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the United States, or is characterized as a form of collective defense undertaken on behalf of the
Iraqi government or another sovereign entity (or collection of entities). Whereas the Islamic State
clearly constitutes an ongoing threat to the security and territorial integrity of Iraq and Syria, the
nature of the threat the Islamic State presently poses to the United States is less direct or
substantial (though arguments could be made that the group currently poses a threat to U.S.
persons and personnel located in Iraq). Importantly, however, if U.S. military action against IS
forces outside Iraq is to be justified as a form of collective defense, it would appear that Iraq or
any other nation that the United States sought to defend would likely need to consent to military
actions that the United States took on its behalf.90
Another possibility for resolving a possible conflict of sovereignty in order to justify the use of
force in Syria without the consent of its government would be to justify intervention on the basis
that Syria is “unable or unwilling” to remove the threat emanating from its territory.91 In present-
day application, it is not clear whether the “unwilling or unable” test is understood to be a
separate test from the Caroline test,92 an additional consideration (for example, an element of
necessity),93 or a substitute for one of the factors, perhaps immediacy in the case of a continuing
threat. In the context of the war against Al Qaeda and the Taliban, the Obama Administration has
indicated that it views as lawful military operations outside of Afghanistan without the consent of
the country in which they take place if a determination has been made that the country is unable
or unwilling to deal with a threat to the United States.94 Although the “unwilling and unable”
doctrine seems to be supported by precedent in U.S. practice, it is unclear whether an
international consensus exists for when or whether it may validly be applied.95
90 Nicaragua v. United States, supra footnote 83, para. 232 (International Court of Justice ruling recognizing that it was
“entitled to take account, in judging the asserted justification of the exercise of collective self-defence ... the actual
conduct of [affected States] at the relevant time, as indicative of a belief by the State in question that it was the victim
of an armed attack ... and of the making of a request by the victim State ... for help in the exercise of collective self-
defence.”). Acts of self-defense taken by U.N. Member States must be “immediately reported” to the U.N. Security
Council. U.N. CHARTER, art. 51.
91 Ashley Deeks, “Unwilling or Unable”: Toward a Normative Framework for Extra-Territorial Self-Defense, 52 VA. J.
INT’L 483 LAW (2012).
92 In fact, the dispute over the Caroline did include as part of the British justification an allegation that the United
States was unable to prevent insurgents from using its territory to launch attacks against British Canada. Id. at 502;
Abraham D. Sofaer, On the Necessity of Pre-emption, 14 EUR. J. INT’L L. 209, 218-19 (2003).
93 See Deeks, supra footnote 91, at 12-13. (suggesting that the “unwilling and unable test” plays a part in the
determination of whether military action is necessary).
94 See, e.g., Harold Hongju Koh, Legal Adviser, U.S. Department of State, Speech before the Annual Meeting of the
American Society of International Law, Washington, DC, March 25, 2010 (listing “willingness and ability of ... states
to suppress the threat the target poses” among factors taken into consideration in deciding whether a targeted killing is
appropriate in a particular country), prepared text available at http://www.state.gov/s/l/releases/remarks/139119.htm;
Attorney General Eric Holder, Speech at Northwestern University School of Law, March 5, 2012 (“the use of force in
foreign territory would be consistent with ... international legal principles if conducted... after a determination that the
nation is unable or unwilling to deal effectively with a threat to the United States.”), prepared text available at
http://www.lawfareblog.com/2012/03/text-of-the-attorney-generals-national-security-speech/#more-6236; Remarks of
John O. Brennan, Assistant to the President for Homeland Security and Counterterrorism, The Ethics and Efficacy of
the President’s Counterterrorism Strategy, Woodrow Wilson International Center for Scholars, April 30, 2012
(“[N]othing in international law that ... prohibits us from using lethal force against our enemies outside of an active
battlefield, at least when the country involved consents or is unable or unwilling to take action against the threat.”),
prepared text available at http://www.wilsoncenter.org/event/the-efficacy-and-ethics-us-counterterrorism-strategy.
95 See TOM RUYS, ‘ARMED ATTACK’ AND ARTICLE 51 OF THE UN CHARTER 455 (2010) (concluding that certain post-
9/11 precedent may support recognition that “attacks by non-State actors may exceptionally constitute ‘armed attacks’
in the sense of Article 51 of the UN Charter, warranting defensive measures when the territorial State is unwilling or
unable to prevent cross-border attacks,” but noting reservations about whether the rule has been established as binding
(continued...)
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Author Contact Information
Michael John Garcia
Jennifer K. Elsea
Legislative Attorney
Legislative Attorney
mgarcia@crs.loc.gov, 7-3873
jelsea@crs.loc.gov, 7-5466
(...continued)
international law); THOMAS M. FRANCK, RECOURSE TO FORCE 64-68 (2002).
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