Blake Williams on “The Spread of War Among Nations: Is Neutrality Enough?”

In another addition to our Ukraine series, LTC Blake Williams further explores an issue briefly raised in the post The Ukraine crisis and the international law of armed conflict (LOAC): some Q & A,  that is, what role, if any, does neutrality law play in the current crisis?

As noted in the previous post, a traditional interpretation of neutrality would say:

A neutral State violates neutrality by breaching its obligation to remain impartial and to not participate in the conflict.  For instance, a State would violate neutrality by supplying warships, arms, ammunition, military provisions or other war materials, either directly or indirectly, to a belligerent, by engaging its own military forces, or by supplying military advisors to a party to the armed conflict.

Given all the war materials the U.S., NATO, and other countries around the world have been providing Ukraine, consider what a scholar concluded in 2015:

[T]he systematic or substantial supply of war materials, military troops, or financial support in association, cooperation, assistance or common cause with another belligerent would make it a co-belligerent.

Yet state practice — which is critical in the development of interpretive norms in international law — in the aftermath of the Ukraine invasion suggests growing support for the heretofore criticized doctrine of “qualified neutrality.”  Basically, it relaxes the legal prohibitions on military aid, but only to those states battling aggression.

Consequently, what we are seeing today suggests to me that, contra to the 2015 (and other) interpretation of traditional neutrality law, the seeming state acceptance of the doctrine of qualified neutrality means even the “systematic” and “substantial” supply of war material to a state that is the victim of aggression does not necessarily make the supplying state a co-belligerent.  Nor does it, alone, provide the aggressor state with a casus belli with respect to the states furnishing the war materials to the country the aggressor victimized. 

Importantly, however, as Blake points out in his essay, the precise parameters of “qualified neutrality” are unclear.

Why?  One reason could be that many scholars (albeit not all) would say neutrality law mainly applies to conflicts between states, and not to the sort of conflicts between states and non-state actors that have up until now dominated international attention in the post-9/11 world.  There just haven’t been enough relevant situations in recent history to develop the “qualified neutrality” concept very much.

Though the long-term implications of this apparent international acceptance of “qualified neutrality” warrant further examination, it nevertheless remains true that even in its current state it has legal limits and policy implications. 

In his very timely essay, Blake offers a perspective on some of those legal limits and policy implications.  The hard question he asks – “Is Neutrality Enough?” – is not a mere academic one, it is a query international lawyers and the policymakers they advise need to ponder now as the tragedy of the Ukraine continues to unfold.

The Spread of War Among Nations: Is Neutrality Enough?*

by LTC Blake Williams, USA

With the failure of deterrence, war has erupted in Ukraine. Although war is a totalizing force that pulls in all authority of a state, the law still bounds it. First, there are rules on the use of force. These rules are designed to guard against the spread of war into the civilian population and to limit adverse effects on civilians. They are familiar to militaries and states. The other set of rules applies to neutrality and is designed to allow states to decide independently whether to involve themselves. These neutrality rules and the principle of qualified neutrality are less familiar. These rules require close examination if NATO states wish to avoid fighting the Russian Army.


The law as customarily understood was laid out in the early 20th Century Hague Conventions V and XIII. These conventions preceded the outlawing of war and have lost much of the relevance following the creation of the League of Nations and then the United Nations. The primary reason for the reduced relevance is the infrequency of international armed conflict between states, which is the only sort of conflict covered by the conventions.


The other reason for diminished relevance is the rise of the application of qualified neutrality. US Attorney General Robert Jackson first established this concept as the US position. Precise interpretations of this concept by states are hard to come by in public writing. However, the general idea is that in a world where war is outlawed, no one is a true neutral.  All states are obliged to support peace; therefore, all states have an obligation to punish the aggressor and favor states acting in defense.

Qualified neutrality defines neutrality violations down in a way that relates them back to the threshold for armed conflict and self-defense. In this way, it seeks to deny that the aggressor gains a right to wage war against those aiding the aggressor’s victims. Exactly what is permitted under the doctrine is unclear. For this reason and others, the doctrine is subject to criticism..


The key rules prohibit belligerent armies from entering neutral territory, restrict recruiting volunteers in neutral territory; require neutrals intern troops belonging to belligerent armies if they enter neutral territory; and generally prohibit states from providing ammunition and war materiel.

Both conventions have denunciation clauses, but the United States, Russia, and all EU member states remain party to the conventions. Because the rules are clearly stated in the conventions, deviations from the rules based on qualified neutrality involve legal risk.


Hague VIII prohibits states from directly sending guns and ammunition to a belligerent. Yet the United States is providing military aid to Ukraine and the EU parliament passed a resolution urging all members to provide military aid.

It appears this is being done under the concept of qualified neutrality. After all, 141 member states in the United Nations have identified Russia as the aggressor in this conflict. Qualified neutrality is the major legal doctrine that allows special support for the victim state.


Who decides on a violation? Because both sides are claiming self-defense in Ukraine, states can join either side in this war and states also have a right to remain neutral. In this context, the belligerents themselves are the judges of who has joined their enemy.

What is the remedy? The belligerents may act against other states according to their perception of the violation and the threat. States are allowed to pursue self-help. Accordingly, legal risks taken in neutrality law translate directly to operational risks.

For instance, in World War II, even though qualified neutrality reasoning permitted lend-lease shipments. The reasoning did not convince the Germany Command. The Germany Navy engaged in self-help by attacking those shipments. Russia might engage in countermeasures against facial violations of neutrality law. If Russia acts violently, NATO states have few response options besides further escalation.


In this world of potential self-help, the law matters somewhat less than deterrence. Western states must carefully assess what response Russia might offer for various facial or actual neutrality violations. They must be ready to accept the operational risks and may need to mitigate these by providing a credible threat of unacceptable outcomes to deter Russian countermeasures.


The Ukrainian borders with NATO states present the greatest risk for expansion of the war. Unless the Ukrainian Army gains the initiative from Russia on the battlefield, Russia will progressively take over Ukraine and drive the Ukrainian Army to the borders.

If the Army flees Ukraine, neutral border states will be required to intern or expel the Ukrainian Army. If the states are unable or unwilling to conduct these tasks, a pursuing Russian Army can enter the neutral territory and attack the Ukrainians where they are. (ICRC Handbook on International Rules Governing Military Operations, p. 413)


Western politicians have made their materiel support for Ukraine clear, and some officials are saying the US will also support an insurgency in the event of a defeat. These plans incentivize Russia to capture or kill resistance fighters.


If the NATO powers want to wage an insurgent campaign, they will likely be unwilling to detain Ukrainian fighters. If Russia wants to destroy the possibility of an insurgency, it will be tempted to pursue and destroy the Ukrainian Army. Indeed, the law contemplates and permits some degree of hot pursuit.

To deter an incursion, NATO will need to assemble a force capable of meeting and repelling a large Russian attack. Even if authorized or encouraged by Putin, a Russian military commander is unlikely to press an attack into a superior opponent, because defeat is an unacceptable outcome.

About the author

LTC Blake Williams is a fellow and instructor with the International Institute of Humanitarian Law in Sanremo, Italy and a US Army Judge Advocate with 16 years of experience. He holds a Masters of Operational Studies with Honors from the US Army Command and General Staff College and Fort Leavenworth; a LL.M from the Judge Advocate General’s Legal Center and School at Charlottesville, Virginia; and a J.D. from the University of South Carolina School of Law.  He is admitted to practice before the Supreme Court of the United States and Court of Appeals for the Armed Forces.


* The views and opinions expressed here are the author’s and do not necessarily reflect the official policy or position of the U.S. Army, the Judge Advocate General’s Corps, the Department of Defense, or any other agency of the U.S. government.

The views expressed by guest authors also do not necessarily reflect the views of the Center on Law, Ethics and National Security, or Duke University.

Remember what we like to say on Lawfire®: gather the facts, examine the law, evaluate the arguments – and then decide for yourself!


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