President Donald Trump’s surprising decision to launch a cruise missile strike on Syria was sharply criticized by Russia as a “flagrant violation of international law.” While it might be tempting to dismiss this claim as mere Putinesque propaganda, on this question at least, Russia is almost certainly correct. In the view of most international lawyers, the US strike on Syria is a crystal-clear violation of the UN Charter. So why doesn’t anybody, except Russia and some international lawyers, seem to care?

The uncomfortable answer seems to be that, at least with respect to this question — can a state use military force against a regime that uses banned weaponry against citizens? — international law simply doesn’t matter very much. And this suits the United States and the Trump administration just fine.

That may sound like an endorsement of lawlessness, or of a Trump administration foreign policy that may be driven by little more than one man’s whim, but it’s actually a worldview that both Democratic and Republican administrations have embraced.

Other nations have apparently embraced it too. As Vox has noted, aside from Russia and Iran — allies of Syria — most states have either supported the Syria attacks or refrained from criticizing them. The leaders of France and Germany, whose nations had strongly opposed the US war against Iraq, issued a joint statement supporting the strikes. Other nations, including countries in the Middle East such as Saudi Arabia, the United Arab Emirates, and Turkey, have also supported them.

Most notably, the Chinese government has carefully avoided any direct criticism of the attack. That’s surprising, given that China had issued vociferous criticisms of the US attacks on Serbia in the legally similar Kosovo crisis, from 1998 to ’99. But in response to questions about the legality of the strike, the official spokesperson for the Chinese Ministry of Foreign Affairs has repeatedly emphasized China’s desire for a political settlement and its strong opposition to the use of chemical weapons, without directly criticizing the US.

This gap between the reactions of governments and those of most international law scholars is striking. If the United States is flouting a law that usefully constrains nations who otherwise might be tempted to go to war, it could be increasing global instability.

On the other hand, if the United States acted correctly in its efforts to deter the further use of chemical weapons by employing military force, then international lawyers may be revealing themselves to be wedded to an outmoded and formalistic ideas about the international system — to a worldview that overrates the sovereignty of nation-states and underrates the lives of people living within them. This argument is made by dissenters from the international law “consensus” view, including Yale’s Harold Koh, the former top lawyer in President Barack Obama’s State Department.

But there is still another, more hard-nosed, realist take on the foreign reaction to the Syria strikes: that the UN’s rules on when force is permitted don’t meaningfully constrain states’ behavior. Although the Trump administration has not formally endorsed this position, I suspect this view is held by many of its decision-makers.

The UN Charter sets out clear rules for when military force is permitted

Before we decide which assessment of the state of international law is correct, it’s worth reviewing the rules and purpose behind the UN Charter’s rules governing the use of force. The UN Charter sets a very high bar. Its Article 2(4) requires member states to refrain “from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the Purposes of the United Nations.”

The charter’s only specific exceptions to this broad prohibition are when a state acts in “collective or individual self defense” (Article 51) or when the Security Council authorizes states to use force in order to “maintain or restore international peace and security” (Article 42). The United States accepted these legal obligations when it ratified the charter back in 1945. That means that the UN Charter is also part of US law, under the Constitution’s provision recognizing treaties as the “Law of the Land.”

The UN Charter’s strict limitations on the use of force were an understandable reaction to the incalculable costs and suffering imposed by World War II. States sought to create a legal framework that would prevent the rise of another aggressor state like Germany and Japan. Though states would still be free to act in their own self-defense (or on behalf of their allies), the UN Security Council was supposed to serve as the main institution responsible for responding to threats to international peace and security.

The text and history of the UN Charter explain why most international lawyers believe the US strikes on Syria last week were illegal. Fifty-nine Tomahawk cruise missiles unquestionably amounts to a “use of force.” And the UN Security Council did not authorize such use of force under Article 42, as it has done in some past conflicts, including the Persian Gulf War.

Nor could the US claim under Article 51 that its missile strike was an act of self-defense, since the chemical weapons attack that sparked the US strike was not aimed at the US or any of its allies. The Syrian government has never directly threatened or actually used its military forces against US aircraft or troops operating to counter ISIS inside Syrian territory.

Not only have scholars concluded that the strikes violated the UN Charter, but many have rejected the possibility of any alternative legal conclusion. It’s not a close case. Marko Milanovic, of the University of Nottingham, spoke for many scholars when he wrote: “I can’t imagine even a remotely plausible argument (let alone a persuasive one) as to why this act is not a breach of Article 2(4) of the Charter.”

Although other experts have been less emphatic, most have agreed with the view, stated here by the top State Department lawyer in the Bush administration, John B. Bellinger III, that “as a matter of international law, President Trump does not have clear authority to use force in response to Syria’s use of chemical weapons.” Michael Glennon, a professor of international law at the Fletcher School of Law and Diplomacy at Tufts University, echoed that sentiment: “It’s … clear that the missile strikes against Syria violated the United Nations Charter.”

There may be a case for humanitarian intervention, but it’s not a legal argument

Koh is the most prominent dissenter from this consensus, arguing that a limited proportionate military action to address a humanitarian crisis can be justified under international law. While Koh concedes the charter’s text does not specifically create such an exemption, he has outlined several conditions under which a state might make a case that it has complied with international law.

First, the behavior it seeks to stop must have “consequences significantly disruptive of international order” — for example, it is creating a refugee crisis, inciting regional disorder, or furthering the spread of chemical weapons. Before acting on its own, the state must have sought action from the Security Council but been blocked by veto. (Both Russia and China have, at various points, vetoed sanctions on Syria.) The intervention must be limited and “for directly humanitarian purposes,” and the effort must be “collective” — a coalition.

“We have reached an international moment when international lawyers in and out of government need to discuss and define a narrow ‘affirmative defense’ to article 2(4),” Koh wrote last week, in a blog post, quoting from a 2016 law review article of his. Such a discussion, he added, “would clarify the contours of an emerging lawful exemption to a rigid rule [that humanitarian intervention is ‘per se illegal.’” Koh said it is too early to tell if last week’s Syria strikes fully meets this standard, but he thinks it very well could.

Despite its moral appeal, his argument has a number of legal weaknesses. There is obviously no textual basis for this interpretation of the charter, but he also cannot cite other familiar tools of legal interpretation to support his view, such as the opinions of the drafters of the UN Charter or the statements of states interpreting these provisions in the years since 1945.

The United States, for instance, has never officially supported such a view of the charter, even during the years when Koh served as its chief legal adviser on international law. (In contrast, the United Kingdom in 2013 made the formal legal case that Syria’s use of chemical weapons that year justified intervention — though almost no other states endorsed its position. In any event, the UK Parliament then voted against taking any military action.)

Critics of Koh’s position have also pointed out that states considered, and rejected, the idea of recognizing such an exception to the UN Charter during the 2005 “Responsibility to Protect” summit of all nations convened by the UN. The resulting “R2P” principle, endorsed by all states, did recognize an international responsibility to prevent and deter humanitarian atrocities, but it also specifically preserved the requirement of approval from the UN Security Council before force can be used for this purpose.

The implications of the supportive international reaction

Assuming, therefore, that the Syria strikes were a clear and obvious violation of the UN Charter, what are we to make of the numerous states that have publicly supported the US military action against Syria?

On the one hand, the toleration of the US action by many states might be evidence supporting Koh’s view that the US action has received a legal exemption from illegality due to its humanitarian purposes and its limited and proportionate nature. International lawyers might argue that this exemption has been established through legal “custom” — if not the letter of the law.

To be sure, the United States has not openly stated this legal position, but it might achieve real support if it did. International law might be really evolving toward Koh’s proposed exemption to the charter. But if the goal of the Trump administration is to promote such an evolution, then its failure to mount a legal defense of its action will only slow progress on that front.

The Trump administration’s actions — and, notably, its failure to issue any legal justification for its use of force — suggests it does not think Article 2(4) is significant or important. After all, the article has not stopped the United States in other cases in which it felt action was necessary. Most international legal scholars believed the US war in Iraq also violated the UN Charter, for example, but this deterred neither the US nor the other states that joined the “coalition of the willing.” Other examples can be cited, such as the aforementioned Kosovo war.

I am not thrilled about an abandonment of Article 2(4), but the Syria strikes shows that the Trump administration is probably right that international law experts treat it with far more reverence than nation-states do. In the United States, for instance, the vast majority of public discussion on the legality of the strikes focused on its legality under the US Constitution. As far as I am aware, no members of Congress have called on President Trump to seek UN authorization for future strikes.

I am not claiming that international law doesn’t matter; all things being equal, states would prefer to act in concert with their international obligations. But there are many powerful nonlegal forces affecting the decisions of states to use or not use military force. Those nonlegal forces include questions of global stability, military capability, support from other key and affected states, and domestic political support. Such factors are always going to be more significant drivers of action than the views of international lawyers.

I am doubtful that the slow degradation of Article 2(4) will, as some have warned, lead to the rejection of all other international laws. States follow international laws for many different reasons. Scholars have argued they do so out of rational self-interest, because they fear injury to their global reputation, or because their domestic politics favors international law compliance. Such factors will continue to support compliance with other areas of international laws such as trade or tackling climate change. But it seems clear those factors do not seem to support strictly abiding by the prohibition on the use of military force in Article 2(4).

For the United States, the most important constraints on the use of force have been, and will continue to be, Congress and US public opinion. Foreign reaction to any strikes is also quite important, but that’s not the same thing as rigid adherence to the UN Charter. UN support would probably have increased the likelihood of US success in Iraq, and no doubt the US will continue to seek such support in Syria and North Korea.

So the UN will not become an irrelevant bystander, but neither will it operate as the final authority on the US decision to use force. This may not be ideal, but one important lesson of the reaction to the Syria strikes is that we should all start getting used to this reduced role for the UN, and stop the unrealistic fetishization of Article 2(4).

Julian Ku is the Maurice A. Deane distinguished professor of constitutional law at Hofstra University School of Law, in New York. He is a co-founder of the international law blog Opinio Juris and a contributing editor to Lawfare.

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