I read Jennifer Trahan’s post yesterday with great interest — but not surprisingly I disagree with it. Before I get to my disagreements, though, I think it’s bizarre that we are all debating the legality of unilateral humanitarian intervention in the context of the recent US missile attack on Syria. It simply beggars belief to think that the attack was in any way motivated by humanitarian concerns. Chemical weapons, which have killed perhaps 2,000 civilians, are not the problem in Syria; conventional weapons, which have killed hundreds of thousands, are the real threat. And the US has done absolutely nothing to protect Syrians from conventional weapons — it has simply funnelled even more into the country to support various rebel groups (including some that are allied with al-Qaeda) in their struggle against Assad. The US cares about protecting its own interests in Syria, such as preventing chemical weapons from being used against Americans. (The real message of the completely ineffectual attack.) It does not care about the lives of ordinary Syrians, as the ever mounting death-toll indicates.
But let’s put aside the context of the missile attack and focus on Trahan’s legal claims. The first is that unilateral humanitarian intervention (UHI) — the qualifier, of course, is critical — can be legal in the right circumstances. The post, however, doesn’t even come close to establishing that claim. Just consider what Trahan cites in defence of it:
 NATO’s intervention in Kosovo, in which “all NATO members supported the intervention designed to stave off ethnic cleansing.” Trahan openly acknowledges that “many did not defend it as ‘humanitarian intervention’ per se, except Belgium” — but that gives away the ballgame. If the 26 other NATO states did not invoke UHI, the attack does not help establish UHI’s legality. As the ICJ pointed out in the Nicaragua case (para. 207), not even the Court itself has the “authority to ascribe to States legal views which they do not themselves advance.” So it doesn’t matter whether Trahan and other scholars would like to describe Kosovo as an example of UHI. All that matters is that NATO states could have invoked UHI but chose not to.
It is also telling that Trahan fails to point out that the Kosovo intervention met with significant international criticism. Here are Vaughan Lowe and Antonios Tzanakopoulos in the Max Planck Encyclopedia:
33 The response of other, non-NATO, States to arguments that there was a legal basis for the Kosovo bombing campaign and for a right of humanitarian intervention was overwhelmingly negative. The Non-Aligned Movement (NAM), numbering well over half of the Member States of the UN, unequivocally condemned the use of force against the (then) FRY, as did many other States, some of which are nuclear powers. In these circumstances, no right of unilateral forcible humanitarian intervention can be said to have emerged as a rule of customary international law.
 UK and US no-fly zones in Iraq. Once again opinio juris is lacking: the coalition initially provided no legal justification for the no-fly zones, and the US later justified them as self-defence (against threats to coalition aircraft, a wonderfully circular argument).
 ECOWAS’s interventions in Liberia in 1990 and Sierra Leone in 1998. Same problem: as Adam Roberts has pointed out, ECOWAS never invoked UHI to justify its actions. It relied instead on provisions in its own founding treaty.
 The UK’s endorsement of UHI in Syria, particularly in the context of the 2013 sarin gas attack that killed hundreds if not thousands. Unlike the other examples, this endorsement does, in fact, contribute opinio juris in favour of UHI.
So, there we have it: one state that explicitly and regularly endorses a right of UHI. And against that, we have the unequivocal rejection of UHI by the 120 states that are part of the Non-Aligned Movement and the 134 states that are part of the Group of 77, which includes major powers like China, India, and South Africa. (The two groups obviously overlap.) How any scholar could conclude that customary international law nevertheless recognises a right of UHI, however limited, is simply beyond me.
For similar reasons, I also reject Trahan’s confident claim that UHI could never be criminal. Here is what she says:
Humanitarian intervention, narrowly construed, then clearly also would not constitute the crime of aggression, which is poised to activate this December 2017 before the International Criminal Court. (Anything in a legal “grey area” is excluded from that definition—and, at minimum, humanitarian intervention (sometimes supported and sometimes invoked) is within that legal grey area. The U.S., a non-State Party to the ICC’s Rome Statute, would be exempt from the crime’s jurisdictional reach, even if it does activate.)
I disagree. To begin with, during the Kampala Review Conference in 2010, states soundly rejected the US’s attempt to specifically exclude UHI from the crime of aggression. Here is the text of the US’s failed Understanding:
It is understood that, for purposes of the Statute, an act cannot be considered to be a manifest violation of the United Nations Charter unless it would be objectively evident to any State conducting itself in the matter in accordance with normal practice and in good faith, and thus an act undertaken in connection with an effort to prevent the commission of any of the crimes contained in Articles 6, 7 or 8 of the Statute would not constitute an act of aggression.
More importantly, the fact that scholars insist UHI can be legal does not make the legality of UHI fall into a “grey area.” On the contrary, it is difficult to imagine any issue that is more black and white given state practice. Article 2(4) of the UN Charter is clear: force is legal only when authorised by the Security Council or in self-defence. UHI does not involve the former by its very definition, and there is no argument de lege lata that UHI can be justified as a form of self-defence, because it does not involve an armed attack on the intervening state. Adil Haque made that point in response to Jens’s recent post, and here are Lowe and Tzanakopoulos again:
23 Humanitarian intervention in order to alleviate the suffering of a local population cannot, without more, be justified as self-defence. Self-defence under Art. 51 UN Charter requires that an armed attack occur against a State. In most cases, widespread violations of human rights will not reach the gravity threshold of an armed attack. Even if the oppression does reach the threshold of an armed attack, however, there will be no armed attack against a State, but at most an armed attack against the population of the State by or with the support or inaction of State authorities. The right to self-defence under international law vests in States and not in sub-State entities such as the local population. Moreover, the oppression will, ex hypothesi, not emanate from another State, but will be by the government upon its own people.
The illegality of UHI under Art. 2(4) is, of course, not set in stone. As Lowe and Tzanakopoulos rightly note, UHI could become legal through subsequent state practice that results in a new interpretation of the provision or (possibly) through the emergence of a supervening customary rule. But that has clearly not happened, given G77 and NAM’s ongoing and unwavering opposition to UHI.
It is unlikely, of course, that the ICC will ever prosecute a government official who is responsible for preparing, planning, initiating, or executing a UHI — and not simply because of the new crime of aggression’s crimped jurisdictional regime. But that does not mean UHI does not manifestly violate the UN Charter. It most certainly does.