The Law of War and the Russian Invasion of Ukraine

The Law of War and the Russian Invasion of Ukraine

Legal Sidebari

The Law of War and the Russian Invasion of
Ukraine
March 16, 2022
In the days after Russia’s invasion of Ukraine on February 24, 2022, many countries condemned the
action as a violation of international law governing when countries may use force against one another.
Since then, several observers, including the U.S. Secretary of State and other foreign government
officials, have cited evidence that the Russian military has targeted civilians, struck protected sites, and
taken other actions that violate international law regulating the conduct of war. This Legal Sidebar
provides a brief introduction to the international legal framework governing the use of force in the
invasion of Ukraine and concludes with a discussion of avenues for accountability and options for
Congress.
Terminology
The law of war generally refers to the portion of international law that regulates the inception of use of
force, the conduct of hostilities, and the protection of war victims, among other things. The term is often
used interchangeably with the law of armed conflict and international humanitarian law. There are two
major categories under the law of war umbrella: jus ad bellum (legal rules governing when a country can
resort to use of force) and jus in bello (law governing conduct during the use of force). While they can be
interrelated, jus ad bellum and jus in bello generally operate independently such that compliance with one
category is required regardless of compliance with the other. For example, a state that is a victim of a jus
ad bellum violation because it is attacked without a lawful basis must still comply with jus in bello when
conducting military operations to defend itself.
Jus ad Bellum: Deconstructing the Justifications for War in Ukraine
The starting point to analyze most aspects of jus ad bellum is the U.N. Charter. Article 2(4) prohibits
member-states from using or threatening to use force against one another, but there are exceptions. Article
51 preserves member-states’ right to act in either individual or collective self-defense when an armed
attack occurs, and Chapter VII of the charter permits the U.N. Security Council to authorize military
actions necessary to maintain or restore international peace and security. A state can also consent to the
use of force in its territory.
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Customary international law (described in this CRS Report) also informs jus ad bellum. Customary
international law requires that the use of force be proportionate to the justification for military action and
necessary because no other reasonable means of redress are available.
Russia’s Jus ad Bellum Claims
The morning of the invasion in Ukraine, Russia’s permanent representative to the United Nations notified
the U.N. Secretary-General of its military action. Appended to the notice was a speech by Russian
President Vladimir Putin describing a host of grievances and justifications for the invasion. While it is not
clear that international law has had any influence on President Putin’s decisionmaking, he nevertheless
couched several justifications using international law and the U.N. Charter’s terminology. Russia’s legal
theories centered on three arguments.
First, Russia claimed to be defending itself from a generalized threat posed predominantly by the United
States and other NATO members but emanating from Ukraine. Article 51 of the U.N. Charter preserves
states’ “inherent right” of self-defense when an “armed attack occurs,” but it does not define the right’s
exact contours. While there are a range of views on how imminent the attack must be before use of force
in self-defense is allowed, observers have generally concluded that the absence of military action in
Ukraine threatening the Russian state means Russia’s self-defense argument is not viable under any
standard.
Second, Russia claimed to be acting in collective self-defense of separatist areas in Ukraine’s Luhansk
and Donetsk regions, which the Russian government recognized as independent states three days before
its invasion. However, the two areas do not appear to satisfy international law’s traditional criteria for
statehood. In particular, legal analysts assert that the areas cannot be considered states because their
purported independence was established through the use of force; they do not exercise control over the
whole of their claimed territory; and they depend upon Russia for economic, financial, political, and
military support. Even if the regions could be considered states, observers note that jus ad bellum
principles of necessity and proportionality would require Russia to limit its military intervention to
actions that protect only these breakaway regions—not a full-scale invasion aimed at the
“demilitarization” of all of Ukraine.
Third, Russia argued that its invasion is designed to prevent “genocide perpetrated by the Kiev regime”
against Russians and Russian-speakers in Ukraine. As discussed in this Legal Sidebar, Ukraine
“emphatically denies” the genocide allegation and has challenged Russia’s assertion before the
International Court of Justice. Neither the United States nor international human rights monitors have
reported evidence of such genocide in their assessments, and most observers view the claim as an entirely
fabricated pretext for overthrowing Ukraine’s government.
Jus in Bello: What Rules Apply During the Conflict?
As the war in Ukraine proceeds beyond the initial invasion to sustained armed conflict, jus in bello
principles become more prominent. Jus in bello is derived from a collection of treaties and customary
international law. Two sets of international agreements, the Hague Conventions of 1899 and 1907 and the
four Geneva Conventions of 1949, form the foundation of the treaty-based portions of jus ad bellum,
although other treaties are also relevant. The Hague Conventions chiefly focus on regulating the means
and methods of warfare, and the Geneva Conventions primarily provide protections for those who do not
take part in the hostilities or can no longer fight. Ukraine and Russia are parties to both core sets of
treaties but not to all of their related protocols. “Grave breaches” of the Geneva Conventions and other
serious violations of jus in bello can constitute war crimes—an issue explored in this CRS Sidebar.
Key jus in bello principles include the following:

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 Military necessity: States engaged in armed conflict may take measures necessary to
accomplish legitimate military objectives, provided international law does not otherwise
prohibit those measures.
 Humanity: Military measures cannot inflict suffering, injury, or destruction that is not
necessary to accomplish a legitimate military objective.
 Proportionality: Parties to a conflict must refrain from attacks expected to cause
incidental harm to civilians or damage to civilian property that is excessive in relation to
the concrete and direct military advantage to be gained. Parties must take all feasible
precautions to avoid or reduce incidental civilian harm.
 Distinction: Parties to a conflict must distinguish between civilians and combatants and
between protected and unprotected objects. Parties cannot direct attacks at civilians or
protected objects.
In addition to these general principles, jus in bello provides special protection to certain groups, such as
civilians, children, certain medical and religious personnel, and voluntary aid workers. It also protects
groups that no longer take part in hostilities, such as the wounded, sick, or shipwrecked or prisoners of
war. Common Article 3 of the four Geneva Conventions adds a “minimum yardstick” of safeguards for
those who do not otherwise have protected status. It prohibits, among other things, torture; cruel
treatment; biological experiments; rape; sexual assault; hostage-taking; and murder, mutilation, or
maiming of those not taking part in hostilities. Certain properties also receive special protection, including
historic monuments; hospitals; buildings dedicated to religion, art, science, or charitable purposes; and
places where the sick and wounded are collected, provided they are not being used for military purposes.
Jus in bello limits the weapons states can use during armed conflict. It prohibits two general categories of
weapons—those that by nature cause superfluous injury or are inherently indiscriminate—and certain
specific weapons, such as poisonous weapons and gases, chemical weapons, and biological weapons. Jus
in bello also regulates the conduct and methods of warfare by prohibiting pillaging, limiting destruction
and seizure of non-military property, requiring free passage of some humanitarian relief, and regulating
the white flag of surrender, among other things.
Jus in Bello in Ukraine
U.S. and foreign government officials and observers have asserted that some of Russia’s alleged actions,
including the following, could constitute violations of the law of war:
 Use of ballistic missiles and other explosive weapons in an indiscriminate manner in
densely populated areas;
 Airstrikes that damaged a Holocaust memorial;
 Artillery, airstrikes, and other attacks on civilians;
 Targeting and seizing nuclear power plants;
 Airstrikes and other attacks on hospitals;
 Attacking and mining agreed-upon humanitarian corridors designed to allow civilians to
evacuate from and humanitarian goods to be brought into areas of active conflict; and
 Use of cluster munitions damaging a civilian hospital, residential neighborhoods, and a
preschool. (While neither Ukraine nor Russia are parties to the Convention on Cluster
Munitions, the munitions’ use could implicate other jus in bello prohibitions.)
Some observers have noted that elements of Ukraine’s conduct are also potentially unlawful. In particular,
the public display of captured Russian soldiers during news conferences could implicate the Third Geneva
Convention’s requirement to treat soldiers humanely and protect them from “insults and public curiosity.”

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Identifying, gathering evidence of, and proving jus in bello violations is a highly fact-specific enterprise
that requires information of on-the-ground circumstances and decisionmaking. It can be especially
challenging to evaluate whether civilian casualties and strikes on civilian infrastructure were intentional
(and therefore unlawful) or incidental and not excessive (and therefore potentially permitted under the
principle of proportionately). The International Criminal Court is collecting evidence of possible war
crimes and other violations of international law in Ukraine. Media outlets, private citizens, and other non-
government groups have amassed user-generated videos of Russian military action that could serve as
evidence of war crimes. Many hurdles to international accountability remain, however, and Russia denies
targeting civilians or violating international law.
Methods for Accountability and Legislative Options
Identifying avenues of accountability for law of war violations raises complex practical, legal, and
jurisdictional questions. As discussed in this Legal Sidebar, Ukraine is pursuing cases against Russia in
the International Court of Justice and other international tribunals, but constraints on jurisdiction and
enforcement may limit the cases’ practical impact. Some observers have called for the creation of a new
international tribunal with broader jurisdiction to address Russia’s actions. Germany and Poland have
reportedly opened investigations into whether the invasion is leading to crimes that can be prosecuted
under their respective domestic laws. The United States has a war crimes statute (18 U.S.C. §2441), but it
does not provide universal jurisdiction, and the Department of Justice has not prosecuted or convicted
anyone for a war crimes offense under this statute. Some commentators have called for Congress to
amend this statute to provide broader jurisdiction. Others have proposed amending the Foreign Sovereign
Immunities Act to allow civil lawsuits against Russia and attachment of Russian assets.
At the U.N., 141 countries voted for General Assembly Resolution ES-11/L.1, which “deplores” the
invasion as an unlawful use of force, but this resolution is nonbinding. Russia vetoed a different
resolution at the U.N. Security Council that would have contained a binding “decision” that Russia must
immediately cease using force and unconditionally withdraw from Ukraine. As examined in this CRS
Insight, U.N. bodies may continue to address aspects of the Russian invasion, and Congress and the
executive branch have avenues to influence (but not control) U.N. action.
Congress could consider legislation directing the United States’ Foreign Claims Settlement Commission
to permit claims arising from Russia’s invasion and its possible nationalization of American-owned
property in Russia. Discussed in this CRS In Focus, the Foreign Claims Settlement Commission is a
quasi-judicial, independent agency within the Department of Justice that adjudicates claims of U.S.
nationals harmed by foreign governments. Its authority is limited to country-specific programs created
through legislation or by referral from the U.S. Department of State.
U.S., European Union, and allied countries have imposed sanctions on Russia in an effort to hold it
accountable for the invasion. Some Members of Congress have advocated for expanding those sanctions.
Members have also introduced legislation that would authorize the President to seize and liquidate
Russian oligarchs’ assets in the United States. The International Emergency Economic Powers Act
(IEEPPA) allows the President to block transactions and “freeze” assets, but the President’s authority to
vest (i.e., take title to) those assets is limited to circumstances when the United States has been attacked or
is engaged in hostilities.

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Author Information

Stephen P. Mulligan

Legislative Attorney

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