[Jennifer Trahan is Associate Clinical Professor, at The Center for Global Affairs, NYU-SPS, and Chair of the American Branch of the International Law Association’s International Criminal Court Committee. The views expressed are those of the author.]

Postings on Opinio Juris seem fairly squarely against the legality of the U.S. missile strike last week into Syria. Let me join Jens David Ohlin (blogging on Opinio Juris) and Harold Koh (blogging on Just Security) in making the contrary case.

When NATO intervened in Kosovo in 1999, member states did not have UN Security Council approval; yet all NATO members supported the intervention designed to stave off ethnic cleansing. True, many did not defend it as “humanitarian intervention” per se, except Belgium, which made the case for the legality of humanitarian interventions in briefing to the International Court of Justice. Still, all NATO members endorsed the military action.

Humanitarian intervention has also been cited as the legal justification for UK and US no fly zones in Iraq, and to justify ECOWAS’s interventions in Liberia in 1990 and Sierra Leone in 1998, prior to UN Security Council approval, which was later forthcoming.

And, after the Assad regime used sarin gas in August 2013, resulting in an estimated 1,400 victims, the UK was prepared to act under the doctrine of humanitarian intervention, arguing that the 3 criteria for intervention were met:

• There is convincing evidence, generally accepted by the international community as a whole, of extreme humanitarian distress on a large scale, requiring immediate and urgent relief;
• it must be objectively clear that there is no practicable alternative to the use of force if lives are to be saved; and
• the proposed use of force must be necessary and proportionate to the aim of relief of humanitarian need and must be strictly limited in time and scope to this aim (ie the minimum necessary to achieve that end and for no other purpose).

So, despite many who would argue there is no such thing as “humanitarian intervention” or it is dead subsequent to the development of the responsibility to protect (R2P), humanitarian intervention keeps being invoked.

Why? Because there are times that UN Security Council dysfunctionality in voting, serves to shield the commission of atrocity crimes. China shielded President Bashir of Sudan while his armed forces coordinated with the Janjaweed militias to commit genocide in Darfur, and Russia has been shielding the Assad regime while it uses sarin and chlorine gas, not to mention other indiscriminate weapons and targeting of civilians. (We should not be outraged only at the regime’s chemical weapons use.)

Therefore, when R2P tells us that “pillar 3” forceful intervention requires UN Security Council approval, as it does, it is failing to do what it set out to achieve—to protect a people in peril from grave atrocities.

Remember, in 1999, Kofi Annan asked the General Assembly:

If, in those dark days and hours leading up to the [Rwanda] genocide, a coalition of States had been prepared to act in defence of the Tutsi population, but did not receive prompt Council authorization, should such a collation have stood aside and allowed the horror to unfold?

The International Commission on Intervention and State Sovereignty gave a helpful response in 2001, not only setting criteria for intervention, but also, noting that if the UN Security Council failed to act, one should not be surprised if others did. The Secretary-General’s 2004 High-Level Panel on Threats, Challenges and Change then went on and also set similar criteria for intervention (as had the Independent International Commission in Kosovo (the “Goldstone Commission” before it).

So for those who claim we don’t know what humanitarian intervention is, these sources and the criteria they articulate suggest that we have a pretty good understanding of it. If we need more clarity as to its parameters to ensure the doctrine is not susceptible to abuse, then, rather than rejecting the doctrine entirely, it should be up to us international lawyers to figure them out.

R2P then backs off its promising start and ultimately concludes that UN Security Council approval is required for any forceful intervention. So, basically in answer to Kofi Annan’s question what to do when there is no UN Security Council approval, it answers: get UN Security Council approval.   This cannot suffice.

Borne out of frustration with this dilemma, the French adopted their initiative “not to veto” in the face of mass atrocity crimes, and 112 states have joined the Accountability, Consistency and Transparency (ACT) Code of Conduct to act in the face of mass atrocity crimes. These were both extremely useful initiatives.

Yet, three of the permanent members of the UN Security Council will agree to neither initiative—Russia, China, and the U.S. I do not lump these countries fully in the same boat, because the US often makes clear the importance of deterring atrocity crimes, while not formally joining the initiatives, which it should.

The day that these hold-out P3’s join the French or ACT initiative, we no longer need to talk about “humanitarian interventions,” because the UN Security Council will be able to function as it was designed under the UN Charter, to both maintain international peace and security and to protect human rights (one of the purposes of the UN).

Another fallacy is that we read the veto as if absolutely anything can be vetoed, when the veto sits within the context of the UN Charter, which imposes obligations; we should explore further what is a legitimate versus an illegitimate veto that should be treated as null and void. The General Assembly could request an advisory opinion from the ICJ on this.

In the meanwhile, the UK has the right approach (as well as the Danish), that we have to leave a small carve out for the legality of humanitarian intervention, when narrowly construed. (The US has previously sometimes invoked what sounds like humanitarian intervention, while not fully formally endorsing the doctrine.)

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.)

It is unclear if the US’s missile strike was intended to fall within the doctrine of humanitarian interventions, as we don’t have a statement of the legal basis, which the U.S. should make clear, as well as what if any follow up plan it has. Harold Koh is right when he writes: “Going forward, all of this will require not just bombs, but diplomacy; not just tweets, but thoughtful diplomatic proposals; not just ‘America First,’ but genuine American multilateral leadership.” Just Security, 4/7/17.

One approach would be appointing a special envoy to pursue diplomatic negotiations, including partition of the country, similar to the partitioning of Bosnia under the Dayton Peace Accords. Republika Srpska iwithin Bosnia was given entity status, yet its military and political leaders were later tried by the Yugoslav Tribunal for atrocity crimes. Clearly, diplomacy and war crimes trials are not mutually exclusive.

President Obama’s “red line” in response to which the US and international community did nothing was shameful. Yet, an argument can be made that at that point in time there was an alternative — to require Assad to relinquish his chemical weapons stocks. And, indeed, some, but clearly not all, of those stocks were destroyed pursuant to the legal regime established. So, by now, what could have been a viable alternative has been pursued, and Assad failed to adhere to it.

It is important to also note that humanitarian intervention can take many forms, and need not mean full-scale intervention, which should always be the last resort. Other forms would include limited no fly zones, protection of civilians in refugee camps, and establishing humanitarian corridors.

Furthermore, unilateral intervention is always the least best alternative. Certainly, endorsement by a regional organization (such as NATO or ECOWAS – as was done in the past), or even multilateral action not endorsed by a regional organization would be preferable. And, if there must be unilateral intervention, it should occur under close consultation with key US allies.

It is far too easy to insist on legal perfectionism and a strict readings of the UN Charter as we sit comfortably typing at our computers. We should not utterly shut the door on a doctrine designed to prevent atrocity crimes when all other means are failing, as they have been in Syria. I agree with Jens David Ohlin that we are “too focused on state sovereignty to the exclusion of any other legal categories” including “the right to be free from genocide and crimes against humanity.” The principles of humanity that have been a guiding principle since the time of Hugo Grotius, and the 1899 Martens clause, should still guide us today to seek a more responsible legal approach, one that does not prioritize sovereignty over humanity.