Turkey’s (Latest) Invasion of Syria: Aggression, Proportionality, and Legal Consequences for NATO and Third-Party States

Turkey’s latest invasion of Syria violates the prohibition of aggression. Its forces and agents have violated the basic rules of international humanitarian law. The moral force of these prohibitions and rules should be obvious, but their legal force may not be fully appreciated. No doubt, Turkey bears State responsibility for its acts. Turkish officials and agents bear individual criminal responsibility as well. These violations also trigger the legal responsibilities of all States. These responsibilities include prosecuting individuals responsible for war crimes as well as doing everything reasonably in their power to ensure respect for the law of armed conflict. But they do not end there.

The prohibition of aggression and the basic rules of international humanitarian law are peremptory norms. In the words of the United Nation’s International Law Commission (ILC), “Peremptory norms of general international law (jus cogens) reflect and protect fundamental values of the international community, are hierarchically superior to other rules of international law and are universally applicable.” Peremptory norms permit no derogation, meaning that nothing can justify their breach.

Serious breaches of peremptory norms, involving gross or systematic violations, give rise to particular legal consequences. All States are legally required to cooperate to bring any serious breach of a peremptory norm to an end by lawful means. Conversely, States are legally prohibited from helping to maintain a situation created by any serious breach.

The United States and Russia must cooperate to end these violations, not block action in the Security Council. The United Kingdom, France, Germany and other States that suspend arms sales to Turkey are simply doing their legal duty. Other States must do theirs.

If Turkish forces clash with Syrian or Russian forces, NATO countries may not come to Turkey’s “defense.” The North Atlantic Treaty does not require them to do so and, in any event, they may not do anything to aid or assist Turkey in maintaining the situation created by its illegal acts.

Presumably, NATO countries will not condemn Turkey simply for using force against a non-State actor on the territory of a non-consenting State. Many NATO countries have done so themselves. Some may argue that the Syrian Defense Forces (SDF) are not responsible for armed attacks against Turkey. Others may argue that Turkey’s use of force is disproportionate, meaning that its overall scale and effects are more than required to achieve any legitimate defensive aim.

If Turkish forces clash with Syrian or Russian forces, NATO countries may not come to Turkey’s “defense.” The North Atlantic Treaty does not require them to do so and, in any event, they may not do anything to aid or assist Turkey in maintaining the situation created by its illegal acts.

So far, most NATO and European Union countries have ignored the law of interstate force (ius ad bellum) altogether and focused on Turkey’s violations of international humanitarian law (ius in bello) (but see here and here). Yet these two branches of international law are interdependent. Turkey may violate the prohibition of aggression by grossly and systematically violating the basic rules of international humanitarian law.

It is true that a use of force may violate the prohibition of aggression without violating the basic rules of international humanitarian law. But the opposite is hardly possible. As Christopher Greenwood (a former judge at the International Court of Justice, among other things) wrote years ago,

an act which contravened the ius in bello could not be a reasonable and proportionate measure of self-defense. In that sense, the rules of the ius in bello give detailed expression to one of the principles of the ius ad bellum.

Each and every murder, rape, and torture committed by Turkish forces and agents is an unlawful use of force that cannot be justified on any theory of self-defense. Taken together, the character, gravity, and scale of these unlawful uses of force can violate the prohibition of aggression.

We sometimes speak as if the law of interstate force applies to a military campaign as a whole, while the law of armed conflict applies to discrete acts of violence. This is a convenient shorthand, not a legal principle (let alone a moral one). A military campaign is just a more-or-less coordinated set of violent acts. The whole is nothing more than the sum of its parts. Military campaigns are legally heterogenous to one extent or another, a mix of lawful and unlawful uses of force. Our focus depends on our purpose. In determining our own legal obligations, our focus should be on serious breaches of peremptory norms.

When we say that some military campaign is lawful overall, we just mean that almost all of its constituent acts of violence are reasonable and proportionate measures of self-defense. If most of its constituent acts of violence grossly and systematically violate basic rules of international humanitarian law, then we should not hesitate to call it aggression. To take an extreme case, a military campaign that begins in self-defense and ends in genocide will at some point in between become aggression.

It should surprise no one that peremptory norms are so interconnected. These norms reflect and protect the fundamental values of the international community not one by one but all together. It is not a question of means and ends. When a State grossly and systematically violates basic rules of international humanitarian law, it departs from any legitimate defensive aim it might have, pursuing non-defensive aims or no aims at all. In this case, Turkey’s purported defensive aims are intertwined with another: to prevent the Kurdish people from effectively exercising their right of self-determination. As it happens, that right reflects a peremptory norm all its own.

Image: Nazeer Al-khatib/AFP/Getty

 

About the Author(s)

Adil Ahmad Haque

Professor of Law and Judge Jon O. Newman Scholar at Rutgers Law School, Author of Law and Morality at War. Member of the editorial board of Just Security. Follow him on Twitter (@AdHaque110).