Neutrality in the War against Ukraine

by | Mar 1, 2022

Law of Neutrality in Ukraine

This contribution briefly addresses the question of whether and to what extent States that are not parties to the war against Ukraine are bound by the law of neutrality. In particular, are these States obliged to refrain from any assistance to Ukraine, including by the supply of military equipment?

The Sources of the Law of Neutrality

The law of neutrality is regulated in two treaties that were adopted at the Second Hague Peace Conference on October 18, 1907. Russia and Ukraine are parties to both. The treaties are

In addition to these legally binding instruments, the law of neutrality is dealt with in Articles 39 to 48 of the 1923 Hague Rules of Air Warfare, the 1994 San Remo Manual on International Law Applicable to Armed Conflicts at Sea, and in the 2009 Manual on International Law Applicable to Air and Missile Warfare.

It is an unsettled issue whether there also exists a set of customary rules supplementing the binding and non-binding instruments, because since the 1990s State practice has been far from uniform. Nevertheless, the fact that the law of neutrality has been included in numerous national military manuals provides sufficient evidence of the general recognition of the continuing validity of the essentials of that branch of the law of armed conflict.

Applicability of the Law of Neutrality

The law of neutrality only applies in situations of international armed conflict (IAC). In an IAC, the parties to the conflict are obliged to respect the sovereignty of neutral States. However, because of the considerably low threshold required for an IAC to come into existence—“any resort to a use of force by one State against another State”—neutral States are bound by the law of neutrality and its core obligations of impartiality only in an IAC of a certain duration and intensity. The isolated position that neutral States are bound by those obligations only in cases of a declared war (a formal state of war) has not found sufficient support by other States.

According to the position taken here, the IAC between Ukraine and the Russian Federation began with the annexation of the Crimean Peninsula in 2014 and the Russian military support of the separatists in Luhansk and Donetsk. That IAC escalated considerably on February 23/24, 2022, when Ukraine was attacked and invaded by Russian armed forces, supported by Belarus. It is therefore safe to hold that at least since February 23/24, the intensity and the foreseeable duration of the armed hostilities are sufficient to justify the conclusion that States not parties to the armed conflict are, in principle, bound by the law of neutrality

Obligations of Neutral States under Hague V and XIII

A neutral State is prohibited from allowing a belligerent party to use its territory as a base of military operations or for any other exercise of belligerent rights. Hague Convention V does not explicitly prohibit a neutral State from supplying a belligerent State with military equipment. Its Article 7 merely deals with the “export or transport, on behalf of one or other of the belligerents, of arms, munitions of war, or, in general of anything which can be of use to an army or fleet” by private actors, which a neutral State “is not called upon to prevent.” This surprising gap in Hague Convention V, however, does not imply a right of a neutral State to supply a belligerent party with such items. Therefore, Hague Convention V implicitly forbids the transfer of weapons and ammunition to a belligerent.

Article 6 of Hague Convention XIII, which addresses naval warfare, explicitly provides that the “supply, in any manner, directly or indirectly, by a neutral Power to a belligerent Power, of war-ships, ammunition, or war material of any kind whatever, is forbidden.” Moreover, the prohibition of supplying a belligerent with military equipment clearly follows from the overall obligation of impartiality of a neutral State, i.e., not to take sides in favor of one belligerent and to the detriment of the other belligerent.

Neutrality and Aggression

Because of the veto of the Russian Federation there has been no decision by the UN Security Council based on Chapter VII of the UN Charter that would allow neutral States to deviate from their obligations under the law of neutrality. Therefore, those States that have supplied, and continue to supply Ukraine with military equipment seem to be acting in violation of their neutral-State obligations.

However, there is a strong view held by several States, including the United States, according to which neutral States are allowed to adopt a position of “qualified” or “benevolent” neutrality, by distinguishing between an aggressor and the victim of aggression. Despite the prohibition of the use of force in Article 2(4) of the UN Charter and of any act of aggression as defined in the 1974 UN GA Resolution, the concept of “qualified neutrality” has remained controversial.

Many, including the present author, have continuously opposed it. They have been willing to accept that concept only in case the UN Security Council has authoritatively identified a specific State as an aggressor. Indeed, State practice has shown that without such an authoritative identification, it is often impossible to consider a given State an aggressor because all too often both sides of an IAC justified their military operations as an exercise of their individual or collective right of self-defense. If neutral States were allowed to absolve themselves from their neutrality obligations by a unilateral determination of the aggressor, the law of neutrality could no longer fulfill its function of effectively preventing an escalation of an IAC.

But there are good reasons to take a more nuanced position vis-à-vis “qualified neutrality.” The present situation in Ukraine is a game changer insofar as:

    • The aggressor State itself prevented the enforcement mechanism under Chapter VII UN Charter to function, although there would have been a sufficient majority within the UN Security Council, with China abstaining and not vetoing a decision.
    • With or without an authoritative classification by the UN Security Council, the Russian military operations against Ukraine are apparent acts of aggression—their justification by the Russian President is devoid of any foundation in the facts and in international law.
    • The number of States condemning the Russian attacks as violations of international law is overwhelming. The fact that the usual suspects—such as China, Cuba, Venezuela—seem to be supporting or sympathizing with the Russian position can be neglected.

Accordingly, the many States supplying Ukraine with military equipment—whether defensive or offensive is irrelevant—are not acting contrary to the law of neutrality, nor are they otherwise committing internationally wrongful acts or aiding and assisting such acts.

It may be that the situation in Ukraine is exceptional and unlikely to repeat itself in other parts of the world. Nevertheless, for the reasons given, neutral States can no longer be bound by an obligation of strict impartiality and a prohibition to supply the victim of aggression with the means necessary to defend itself against an aggressor State that is obviously determined to ignore core principles and rules of international law. If the notion of a “rule-based international order” is to be of any significance, States continuing to rely on and believe in international law can no longer stand by and allow an aggressor government to pursue its apparently illegal aims—even if they are threatened by the aggressor with “strategic responses.”


Wolff Heintschel von Heinegg holds the Chair of Public Law, in particular Public International law, European Law and Foreign Constitutional Law at the Europa-Universität Viadrina in Frankfurt (Oder), Germany.