On April 6, the United States unilaterally used force in Syria, against President Assad’s regime, in response to Assad’s alleged use of chemical weapons against a Syrian town and region.  Despite a humanitarian crisis that has been ongoing in Syria for several years, the United Nations Security Council has remained deadlocked, in light of the Russian and Chinese veto regarding any resolution that would have authorized a multilateral use of force.  The United States thus acted alone – potentially breaching both international and domestic law.  This post will examine the legality of United States’ actions under international and domestic law. 

Article 2(4) of the United Nations Charter prohibits states from using force against the territorial integrity or political independence of another state.  The only two exceptions to this general ban on the use of force involve Security Council authorization and self-defense.  The United States’ use of force in Syria had not been authorized by the Security Council, because, as mentioned above, Russia and China have persistently threatened or used their veto power to block resolutions regarding Syria.  Moreover, the United States’ use of force in Syria was not an instance of self-defense.  States can use force in self-defense if they are under an armed attack, or if they are about to be attacked; Syria has not threatened any other nations, and certainly not the United States, and the latter was not in danger of an imminent attack by Damascus.  Thus, under a traditional interpretation of international law, the United States has used force illegally in Syria, in breach of treaty and customary international law. 

It should be noted that the United Nations Charter is a treaty, to which the United States is a party.  The obligation in Article 2(4), mentioned above, is a treaty provision which binds the United States.  Thus, this treaty provision would be considered as “supreme Law” of the land under Article VI of the U.S. Constitution.  As such, this provision becomes part of United States’ domestic law and binds the United States on the domestic level as well.  Congress can, under the so-called later-in-time rule, pass a federal statute which trumps an otherwise binding treaty provision.  However, Congress has very rarely done so regarding existing treaties (doing so would put the United States in breach of its international law obligation), and Congress has certainly not done so in this instance, regarding the use of force in Syria. 

Moreover, under domestic law, a United States President is supposed to ask authorization from Congress before using military force in another country.  As Marty Lederman has explained recently, there are three major theories as to when the President can use force unilaterally against another sovereign nation and without Congressional authorization:

“(i) almost never (i.e., only to repel actual attacks, and then only as long as Congress is unavailable to deliberate)–what one might call the “classical” position;

(ii) virtually always, up to and including full-scale, extended war–that was John Yoo’s position, adopted by OLC in the Bush Administration, at least in theory; and

(iii) only under a set of complex conditions that do not amount to “war in the constitutional sense,” and only in conformity with legal restrictions Congress has imposed (including the War Powers Resolution)–a middle-ground position that I denominated the Clinton/Obama “third way,” and which in effect has, rightly or wrongly, governed U.S. practice for the past several decades.”

Marty Lederman had, in a 2013 post, elaborated as follows on the middle ground view:

“Between these two categorical views is what I like to call the Clinton/Obama “third way”—a theory that has in effect governed, or at least described, U.S. practice for the past several decades.  It is best articulated in Walter Dellinger’s OLC opinions on Haiti and Bosnia, and in Caroline Krass’s 2011 OLC opinion on Libya.  The gist of this middle-ground view (this is my characterization of it) is that the President can act unilaterally if two conditions are met:  (i) the use of force must serve significant national interests that have historically supported such unilateral actions—of which self-defense and protection of U.S. nationals have been the most commonly invoked; and (ii) the operation cannot be anticipated to be “sufficiently extensive in ‘nature, scope, and duration’ to constitute a ‘war’ requiring prior specific congressional approval under the Declaration of War Clause,” a standard that generally will be satisfied “only by prolonged and substantial military engagements, typically involving exposure of U.S. military personnel to significant risk over a substantial period” (quoting from the Libya opinion).”

Assuming that the middle ground view is correct- that the President can decide to use force without Congressional approval in limited circumstances – the current use force against Assad cannot be easily justified.  As others have pointed out, the closest precedent for the unilateral use of force in Syria may be the United States’ and NATO use of force in Kosovo in 1999, under the Clinton Administration.  The United States never advanced a legal rationale for its use of force in Kosovo, relying instead on a policy argument that Kosovo was sui generis.  Kosovo was arguably a better case than Syria, because the military intervention in Kosovo had been staged by NATO, not by the United States acting alone, and because the United Nations had already been involved in Kosovo, unlike in Syria.  Thus, Kosovo may not provide the best precedent for Syria.  In addition, adopting the above-mentioned middle ground view on the President’s ability to use force unilaterally, it is difficult to argue that the use of force in Syria will serve significant national security interests, such as self-defense or the protection of American nationals.  It remains to be seen whether the United States’ use of force in Syria will entail an extensive and prolonged military engagement, requiring Congressional approval, or if it will instead be comprised of a time-limited and precise series of strikes not involving exposure of United States’ military personnel.  As of today, however, it is difficult to argue that President Trump should not have sought Congressional approval for the use of force in Syria.

Can the United States’ military actions in Syria be justified on either the international or domestic planes?  First, regarding international law, Harold Koh has argued that the unilateral use of force against a sovereign state can at times be justified under the developing norm of humanitarian intervention.  According to Koh, the following conditions must be met in order for a state to be able to invoke the humanitarian intervention exception to international law’s general ban on the use of force:

“(1) If a humanitarian crisis creates consequences significantly disruptive of international order—including proliferation of chemical weapons, massive refugee outflows, and events destabilizing to regional peace and security—that would likely soon create an imminent threat to the acting nations (which would give rise to an urgent need to act in individual and collective self-defense under U.N. Charter Article 51);

(2) a Security Council resolution were not available because of persistent veto; and the group of nations that had persistently sought Security Council action had exhausted all other remedies reasonably available under the circumstances, they would not violate U.N. Charter Article 2(4) if they used

(3) limited force for genuinely humanitarian purposes that was necessary and proportionate to address the imminent threat, would demonstrably improve the humanitarian situation, and would terminate as soon as the threat is abated.

In particular, these nations’ claim that their actions were not wrongful would be strengthened if they could demonstrate:

(4) that the action was collective, e.g., involving the General Assembly’s Uniting for Peace Resolution or regional arrangements under U.N. Charter Chapter VIII;

(5) that collective action would prevent the use of a per se illegal means by the territorial state, e.g., deployment of banned chemical weapons; or

(6) would help to avoid a per se illegal end, e.g., genocide, war crimes, crimes against humanity, or an avertable humanitarian disaster, such as the widespread slaughter of innocent civilians, for example, another Halabja or Srebrenica. To be credible, the legal analysis of any particular situation would need to substantiate each of these factors with persuasive factual evidence of: (1) Disruptive Consequences likely to lead to Imminent Threat; (2) Exhaustion; (3) Limited, Necessary, Proportionate, and Humanitarian Use of Force; (4) Collective Action; (5) Illegal Means; and (6) Avoidance of Illegal Ends.”

It is unclear whether these conditions have been met in Syria – for example, it is unclear that the Trump Administration is acting consistently with condition 3, and it is unquestionable that the American unilateral action does not satisfy condition 4.  Moreover, Koh’s proposed framework is doctrinal in nature and does not reflect the current status of international law – unless one assumes that Syria is a law-breaking moment and that the evolution of international law requires the breaking of existing international law norms (a point of view which many scholars would disagree with).  Finally, it is also unclear that the use of chemical weapons is prohibited in non-international armed conflict; chemical weapons are banned in international armed conflict and their use is certainly morally abhorrent, but it is not legally clear that chemical weapons are always prohibited in internal and non-international warfare (the use of chemical weapons in international armed conflict is not prohibited by treaty law although it may be argued that it is prohibited under customary law).  And, even if chemical weapons were prohibited in non-international armed conflict, a violation of jus in bello does not provide justification for the use of force against a sovereign state – a point which Koh’s framework ignores (arguably because Koh’s framework focuses on the protection of human rights, which justifies the conflation of jus in bello and jus ad bellum norms). 

On the domestic level, the United States’ use of force in Syria could be justified if one adopts the Yoo/Bybee view, that President can always act alone, without Congressional approval, or if one adopts the middle ground view and concludes that the action in Syria advances national security interests and is so limited in time and scope that it falls outside of a traditional “war.”  As mentioned above, it is unclear as of today what the Syrian military action will entail and it is uncertain whether the strikes will remain limited in duration and scope and whether United States’ military personnel will not be exposed. 

Thus, it is difficult to construct the legal argument that the United States’ use of force in Syria is legal under both international and domestic law.  While military action may be the morally correct response to Assad’s slaughtering of civilians, it appears that the United States’ actions lack a solid legal basis.