Was Trump’s Bombing Syria Legal—And Does It Matter?

On April 7, President Trump ordered a cruise missile attack on a Syrian airbase in retaliation for the Assad regime’s use of chemical weapons against civilians. Policy questions loom large. How, if at all, can Trump’s decision as president be reconciled with his prior warnings—both as a private citizen and as a presidential candidate—that escalating U.S. involvement in the Syrian civil war would constitute a threat of direct conflict with Russia? What will Trump do if Assad uses chemical weapons again? Does the Trump administration have a plan or even the capacity (in light of a demoralized and understaffed State Department) to follow up the gunboat part of its gunboat diplomacy with the diplomacy part?

Meanwhile, critics have raised doubts about the lawfulness of the U.S. action under our own Constitution and international law. Are those doubts justified? If the cruise missile strike was unlawful, might it have been justified nonetheless?

Domestic Constitutional Law

Article I of the U.S. Constitution assigns primary responsibility for going to war to Congress, not the president. Writing in The Atlantic, University of Baltimore law professor Garrett Epps spelled out why the president’s decision to bomb Syria without consulting Congress could be deemed unlawful. Although the president has the authority to act unilaterally to, in James Madison’s phrase, “repel sudden attacks,” Assad’s horrific use of chemical weapons against civilians was not a sudden attack against the United States.

Nor did Congress authorize the use of military force against Assad at some point in the past. Over the last decade and a half, the Bush, Obama, and now Trump administrations have purported to find broad war-fighting authority in two congressionally enacted Authorizations for the Use of Military Force (AUMFs), one passed shortly after 9/11 and the other passed in 2002 authorizing the invasion of Iraq. But even reading those authorizations for all they are worth, they do not authorize military action against Assad.

True, the U.S. has been (mostly indirectly) fighting ISIS in Syria and Iraq, but ISIS is an outgrowth of the Iraq War and thus military action against ISIS arguably falls within the ambit of the 2002 Iraq AUMF. Moreover, ISIS is a lineal descendant of an organization once known as al-Qaeda in Iraq, which could be said to render the action within the scope of the post-9/11 AUMF as well.

Yet fighting ISIS in Syria is different from fighting the Assad regime. The campaign against Assad grows out of the Arab Spring movement. Assad attacked non-violent protesters, leading the latter to take up arms. Some of the anti-Assad fighters are tied to groups that the U.S. may be fighting pursuant to the earlier AUMFs, but fighting Assad cannot be plausibly described as fighting Assad’s enemies.

Thus, President Trump appeared to lack any domestic authority to order bombing the Syrian airfield.

Another argument—put forward most forcefully by Georgetown University law professor Martin Lederman—begins with the proposition that the United Nations Charter restricts the circumstances under which nations may lawfully use military force. The United States is a party to the U.N. Charter, and thus by using force in violation of a valid treaty without obtaining any superseding authority from Congress, President Trump acted unlawfully for domestic purposes. This conclusion depends on the further conclusion that the cruise missile attack was unlawful under the U.N. Charter. Hence, I shall subsume my analysis of Professor Lederman’s contention within my analysis of the international law question.

International Law

The argument for the illegality of the cruise missile strikes under international law is quite straightforward. Article 51 of the U.N. Charter reserves to member states “the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations,” while Articles 39-50 specify how the Security Council can authorize other uses of armed force. Unless either self-defense or mutual defense in response to an armed attack or authorized by the Security Council, the use of military force violates the U.N. Charter as aggression. The Charter permits humanitarian interventions, but only where authorized by the Security Council.

The foregoing account of the U.N. Charter’s restriction of military force reflects the conventional wisdom. However, some activists, government officials, and scholars criticize the conventional wisdom on the ground that Russia’s and China’s willingness to exercise their veto power to block humanitarian interventions means that atrocities go undeterred.

Syria itself is a prime example. Russia regards Syria as a client state and stands prepared to veto any Security Council resolution authorizing military force against the Assad regime, despite the fact that the regime is committing atrocities. But because these atrocities are not armed attacks “against a Member” state, they do not trigger the right of self-defense under Article 51.

As an argument for amending the U.N. Charter, the foregoing critique has considerable force. But the U.N. Charter has not been amended to allow humanitarian interventions absent Security Council authorization or a plausible claim of national or collective self-defense against an armed attack on a member state. Nonetheless, some people argue that the existing charter ought to be construed as allowing humanitarian interventions.

Yale law professor (and former Yale Law School Dean and former State Department Legal Adviser) Harold Koh is the leading such voice, although hardly the only one. In the past several decades, Koh and some other highly respected scholars have argued that states may use military force pursuant to customary international law. In the immediate aftermath of the recent airstrike on Syria, Koh wrote that perhaps it could be legally justified as falling within such a norm. Citing his own scholarship, Koh listed criteria that would need to be satisfied to warrant humanitarian intervention to protect civilian populations even absent Security Council authorization.

Yet, as Professor Lederman quickly noted, the Trump strike against Assad’s airbase did not even satisfy all of Koh’s own criteria. In particular, it was unilateral rather than multilateral. Even more fundamentally, Lederman argued that Koh’s test is aspirational. A proposition does not rise to the level of customary international law if it is as widely contested as the claimed power of humanitarian intervention is.

My Cornell Law School colleague Professor Jens Ohlin has offered a number of different routes to reach the same conclusion as Professor Koh. For example, instead of relying on a customary international law exception to the U.N. Charter, Ohlin contends that Article 51 itself implicitly accepts that behind the Charter stands “natural law.” After all, Article 51 does not grant a right to self-defense; rather, it recognizes the “inherent” right to self-defense. In what does that right inhere? Ohlin says it inheres in natural law, which also protects an inherent right of civilian populations to self-preservation. Thus, as Ohlin would have it, although the Charter does not specifically recognize the lawfulness of humanitarian interventions, its recognition of the existence of one right that comes from outside the Charter (self-defense) implies the possibility of others (such as the right of civilian populations to assistance in the form of humanitarian interventions).

Koh and Ohlin are both first-rate scholars of international law. So are various others who argue for the legality of humanitarian interventions, such as Fordham law professor Thomas Lee. Nonetheless, the view that the Syrian airstrikes were lawful is a distinctly dissident one.

Does It Matter?

Well so what? Even if domestic constitutional law and international law forbade the Trump administration’s attack on the Syrian airbase, perhaps it will lead Assad to hesitate before committing further atrocities. Law imposes obligations, but there are circumstances in which moral obligations should prevail over legal ones. With even some of President Trump’s harshest domestic critics praising his action against Assad, might this be such a case of morally justified illegality?

The answer could differ in the domestic and the international spheres. For decades, Congress has acquiesced in the president’s gradual accretion of power to use military force without prior consultation. As Justice Robert Jackson presciently observed in 1952 in the Steel Seizure Case, “power to legislate for emergencies belongs in the hands of Congress, but only Congress itself can prevent power from slipping through its fingers.” Put differently, Congress has tools it can use to pressure presidents to seek approval before undertaking humanitarian (or other) military interventions; its failure to use those tools can be taken as a kind of tacit consent.

But if the president’s failure to consult Congress can be set aside as a mere technical constitutional violation, the stakes under international law are different.

The argument for humanitarian intervention is not simply problematic as an account of existing international law; it is hardly clear that a world with a norm permitting states to use military force for humanitarian purposes without Security Council approval would be better than the world described by the conventional wisdom.

The Security Council includes illiberal states like Russia and China because of the Council’s vital role in preventing great-power conflict. Disallowing military intervention to stop a genocide is a grave harm, but allowing military intervention by one great power over the objections of another great power might be a catastrophic harm, because it risks great-power military conflict and even nuclear annihilation. Thus, even if it were practically possible to amend the U.N. Charter to allow humanitarian interventions over the objections of great powers, it is not obvious that such an amendment would be wise.

Beyond the risk of great-power war, critics of humanitarian interventions that lack the blessing of the Security Council note that a norm permitting such interventions could be and likely would be invoked pretextually. Mussolini, Hitler, and other monsters offered nominally moral justifications for aggression against other states. Although such actions were not actually justified on humanitarian grounds, a norm that forbids any unilateral such interventions makes it more difficult for aggressors to pretend to comply with international law.

Finally, there is a risk that attempts to justify humanitarian interventions outside of the Security Council process will backfire. For years, unilateralists like John Bolton have argued that international law is not real law and should not prevent a great power like the United States from taking actions that are in its interests. Scholars like Koh, Ohlin, and Lee strongly disagree with the likes of Bolton. They want to see humanitarian interventions permitted precisely because they want to enforce the underlying norms—such as the Chemical Weapons Convention—that Assad and other dictators violate. Yet ironically, such interventions, if accomplished outside of the Security Council process, could vindicate the cynical view of the unilateralists who seek to undermine international law.

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