March 28, 2022
U.S. Nationals and Foreign Military Service
Background
charged with treason (18 U.S.C. §2381). The enlistment in
International law grants rights to and imposes duties upon a
foreign service prohibition does not apply to citizens of
neutral state during an armed conflict between belligerent
countries at war with the United States, except to the extent
nations. One of these duties is that neutral states shall not
they enlist others. The prohibition also does not apply to
furnish troops to belligerent states, except this duty does not
transient nationals of belligerent countries. Agreeing with
include independent actions by a neutral state’s citizens. A
non-state groups to travel overseas and engage in an
state’s neutrality is usually unaffected if its citizens
insurgency is not covered by the foreign enlistment law.
willingly serve in a belligerent state’s armed forces.
International law permits such service, but a state’s internal
Expatriation
law may prohibit it. U.S. nationals (including both citizens
Congress has the power to designate certain voluntary acts
and other persons owing allegiance to the United States (8
by U.S. nationals as expatriating, whereby committing
U.S.C. §1101)) have performed foreign military service at
those acts would result in the loss of U.S. nationality. Since
various times since 1788. This In Focus examines the laws
1941, one such expatriating act has been service in the
governing U.S. national foreign military service during
armed forces of a foreign state under specific conditions.
armed conflicts.
The exact conditions necessary for foreign military service
to be expatriating have changed over time, notably with the
Neutrality Act of 1794
enactment of the Immigration and Nationality Act of 1952
The principle that a state may lose its claim to neutral status
(INA) and the 1986 amendments to the INA. One consistent
if it fails to prevent in its territory a belligerent state’s troop
requirement, however, is that any such foreign military
recruitment or military expeditions is a contribution to
service must be voluntary—actions taken under duress will
international law originally posited by the United States in
not result in expatriation. The Department of State, in its
1793 through George Washington and Thomas Jefferson. A
Foreign Affairs Manual (FAM), states that conscription into
year later, this principle became federal law as part of the
a foreign military, while not dispositive, “will be considered
Neutrality Act of 1794. Observers debate whether the
as a factor highly relevant to possible duress.”
principle of neutrality continues to be viable as customary
international law. The Neutrality Act remains enforceable,
Historical Expatriation for Foreign Military Service
however, and generally prohibits the fitting out of vessels of
Under Section 401(c) of the Nationality Act of 1940 (1940
war or the launch of an expedition from a U.S. territory to
Act), U.S. nationals would lose their nationality by serving
engage in hostilities abroad.
in the armed forces of a foreign state (1) unless expressly
authorized by U.S. law and (2) only if the U.S. national had
Among other things, the Neutrality Act prohibits persons
or acquired the nationality of the foreign state. Individuals
within the jurisdiction of the United States from enlisting in
who were not—or did not become—nationals of the foreign
foreign militaries (18 U.S.C. §959):
state were not subject to expatriation.
Whoever, within the United States, enlists or enters
In 1952, Congress repealed the 1940 Act and replaced it
himself, or hires or retains another to enlist or enter
with the INA. As originally enacted, Section 349 of the
himself, or to go beyond the jurisdiction of the
INA provided that U.S. nationals would lose their
United States with intent to be enlisted or entered in
nationality by serving in the armed forces of a foreign state
the service of any foreign prince, state, colony,
unless such service was “specifically authorized in writing”
district, or people as a soldier or as a marine or
by the Secretaries of State and Defense. In contrast to the
seaman on board any vessel of war, letter of
1940 Act, the INA required case-by-case authorization,
marque, or privateer, shall be fined under this title
which, per the FAM, “appears never to have been granted.”
or imprisoned not more than three years, or both.
The INA removed the exception for service performed by
individuals who were not also nationals of the foreign state,
This law apparently applies to anyone in the United States
instead applying the provision equally to all U.S. nationals.
who joins a foreign military but not those who enlist while
The INA created a new exception, however, for individuals
in another country. Accepting a commission while in U.S.
who entered foreign military service before the age of 18,
territory from a nation at war against a state with which the
providing for expatriation only if such individuals
United States is at peace is also prohibited, but this law
voluntarily remained in the foreign military service after
applies only to U.S. citizens (18 U.S.C. §958). The United
turning 18.
States has historically prevented enlistment and
appointment activity by other nations within U.S. territory,
Current Law
but it has rarely enforced these prohibitions against
Since Congress amended the INA in 1986, a U.S. national
individuals. On the other hand, U.S. nationals serving in the
who enters or serves in the armed forces of a foreign state
military of a nation at war with the United States can be
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will be expatriated if (1) those armed forces are engaged in
with regular retired status and will discontinue retired pay
hostilities against the United States or (2) the U.S. national
(DOD 7000.14-R, Vol. 7B, §060502). Reserve retirees
serves as a commissioned or non-commissioned officer
entitled to retired pay, but not yet eligible to receive it, are
(8 U.S.C. §1481). The 1986 amendments also removed the
barred from FMS (called gray area retirees as retirement
requirement that such service be approved by the
occurs before retired pay starts, usually at age 60). Reserve
Secretaries of State and Defense but required that an
retirees receiving retired pay are not barred; their FMS is
individual intend to relinquish U.S. nationality.
restricted. Reserve retirees forfeit retired pay, if, while
receiving pay, FMS is performed (1) as a commissioned or
As noted in the FAM, the State Department has determined
noncommissioned officer or (2) for a nation engaged in
that voluntary service in the armed forces of a state engaged
hostilities against the United States (Ibid, §060401; see also
in hostilities against the United States is “strong evidence of
8 U.S.C. §1481(a)(3)). Being a citizen of the FMS country
intent to relinquish U.S. citizenship.” In addition, it has
has no effect on an emoluments clause prohibition; consent
interpreted armed forces of a foreign state under the INA to
from Congress is still required for this service. Multiple
include the forces of unrecognized states but not
citizenship by itself is not a basis for discontinuing or
paramilitary organizations.
forfeiting military retired pay. However, regular retirees
who renounce U.S. citizenship may not receive pay, but
U.S. and International Law
reserve retirees, as well as disability retirees, who renounce
Although the United States has never prosecuted anyone
U.S. citizenship would continue to receive retired pay (Ibid,
under the War Crimes Act (18 U.S.C. §2441), U.S.
Vol. 7B, §§060101, 060401).
nationals serving in a foreign military should be aware
certain conduct may be considered a war crime. The Act
Authorized Foreign Military Service (FMS)
prohibits certain breaches of the Geneva Conventions of
Congressional consent is granted for FMS by military
1949, including Common Article 3, and other international
retirees in newly democratic nations (10 U.S.C. §1060).
agreements. These crimes include violations of obligations
The Secretary concerned and the Secretary of State must
during war to protect civilians, prisoners, and other
approve it (22 C.F.R. Part 3a). Former servicemembers with
protected persons, as well as civilian property not used for
no military status and not entitled to military retired pay can
military purposes. War crimes include certain conduct
perform FMS on the same basis as a U.S. national who
against combatants, such as a perfidious attack or misuse of
never served in the armed services, with some exceptions
a flag of truce or emblems of the Geneva Convention (see
(see “U.S. Intelligence Personnel”).
CRS Legal Sidebar LSB10709, War Crimes: A Primer, by
Jennifer K. Elsea). U.S. nationals assisting a belligerent
Foreign Government Employment (FGE)
state would also be subject to other extraterritorial federal
Congressional consent is granted for FGE by regular
laws. Table 1 includes salient offenses.
retirees, gray area retirees, and reserve component
members (P.L. 95-105, §509). FGE is approved through the
Table 1. Selected Extraterritorial Federal Offenses
same process as authorized FMS (22 C.F.R. Part 3a). A
reserve member who accepts unapproved FGE would be
18 U.S.C.
Offense
subject to military discipline. Regular retired pay is reduced
§175
Prohibitions with respect to biological weapons
by the compensation received if the FGE is not approved
(DOD 7000.14-R, Vol. 7B, §050404). Military departments
§229
Prohibited activities (chemical weapons)
must submit annual reports to Congress of FGE approved
for retired general or flag officers (37 U.S.C. §908).
§956
Conspiracy to kill ... in a foreign country
§1091
Genocide
U.S. Intelligence Personnel
Since 2014, former employees, contractors, and
§1203
Hostage taking
servicemembers of the intelligence community (IC) were
§1651
Piracy under law of nations
required to report their FMS and FGE in the two years after
occupying a covered position, which is any IC role with
§2332a
Use of weapons of mass destruction
access to intelligence sources or methods information (50
U.S.C. §3073a). In March 2022, Congress replaced this
§2340A
Torture
reporting rule with a 30-month ban on FMS and FGE (P.L.
Source: CRS analysis of Title 18, U.S. Code, Part I–Crimes.
117-103, Division X, Title III, §308). The Director of
National Intelligence can grant waivers to the IC ban but
U.S. Military Personnel
not to an emoluments clause prohibition. Individuals
Among other prohibitions, the emoluments clause in the
violating this ban may be fined or prosecuted, and their
U.S. Constitution bars all servicemembers from foreign
security clearance is to be revoked by the head of the IC
military service (FMS) without congressional consent (U.S.
element concerned.
Const., art. I, §9, cl. 8). They “must give the government
their unclouded judgment and their uncompromised
Jennifer K. Elsea, Legislative Attorney
loyalty” (18 Op. O.L.C. 13, p. 18, March 1, 1994). The
Jonathan M. Gaffney, Legislative Attorney
FMS bar applies to active, reserve, and national guard
Alan Ott, Analyst in Defense and Intelligence Personnel
forces, as well as all regular component and certain reserve
Policy
component retirees from these forces. Also, the Department
of Defense (DOD) deems unauthorized FMS inconsistent
IF12068
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U.S. Nationals and Foreign Military Service


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