In her recent blog discussing the relevance of the Kosovo precedent in the context of the United States missile strike in Syria, Professor Ashley Deeks noted that “such an intervention, even if narrowly tailored, is very difficult to defend as consistent with international law. Therefore, the United States will have to make the case that the intervention bears moral legitimacy, and it has begun to do so using the same kinds of factor-based arguments we saw NATO member states use in Kosovo to defend the legitimacy of their intervention there.”

I agree that the United States must morally justify the intervention, as there is no legal basis for the cruise missile strikes in Syria under the United Nations Charter use of force paradigm. Ambassador Nikki Haley articulated as much by stating “when the United Nations consistently fails in its duty to act collectively, there are times in the life of states that we are compelled to take our own action.” In other words, the United States’ moral obligation to intervene in Syria outweighed a technical reading of the law.

As Professor Deeks highlights, the United States may eventually attempt to shroud this moral justification in legality by arguing that the missile strikes were part of a humanitarian intervention to protect the Syrian people from Assad’s chemical weapons. Under this controversial use of force theory, moral legitimacy equates to legal justification for military action. Some have made efforts, most notably the United Kingdom following the Syrian use of chemical weapons in 2013, to outline conditions that trigger the right to intervene. However, these criteria are not widely accepted and decisions to use military force for humanitarian purposes remain subjective and inherently political.

The Russian involvement in the Ukraine is illustrative of this point. In March 2014 Russia invaded the Crimean peninsula, a recognized territory of the Ukraine, and occupied the region. Then-Ambassador to the United Nations Samantha Powers condemned the act by stating the “intervention is without legal basis—indeed it violates Russia’s commitment to protect the sovereignty, territorial integrity, and independence of the Ukraine.” Vladimir Putin, on the other hand, claimed the intervention, in large part, was for humanitarian purposes including to protect Russian-speaking minorities and to stop anti-Semitic violence.

While Putin’s justifications were easily dispelled, his response was that of a humanitarian interventionist. Here lies the problem with these types of moral-based use of force decisions: they are inherently subjective and, consequently, easily abused. For example, why is there an obligation to stop the use of chemical weapons in Syria but not to stop the daily atrocities committed in North Korean work camps? When does the moral responsibility that justified an intervention end? Why do certain states have a moral imperative to act while others do not? This lack of clarity empowers states to make these determinations unilaterally and results in divergent views on the appropriate use of force. Even more dangerously, this ambiguity allows a state with nationalistic goals to act with aggression under the pretext of a moral obligation.

This is not a new problem. The drafters of the United Nations Charter decided the best way to “save succeeding generations from the scourge of war, which twice in our lifetime has brought untold sorrow to mankind” was by preventing unilateral state action. To do this, they included Article 2(4) which states that “all members shall refrain in their international relations 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.” This rule only has two exceptions—if the United Nations Security Council collectively authorizes military action or if a state invokes their inherent right of individual or collective self-defense. Outside of this framework, any use of force is unlawful.

As I have previously written, the Charter is careful to separate the moral and legal right to use force. The unprecedented destruction of the World Wars, coupled with the ineffective earlier attempts to end wars of aggression, demonstrated to the international community a need for a collective body to maintain peace and security. This resulted in the drafting of the United Nations Charter and its clear use of force framework. The document deliberately centralizes use of force decisions as, when given discretion to independently wage war, a state will often act for selfish reasons. The Charter attempts to stop this behavior by requiring strict compliance regardless of a state’s subjective intent or perceived moral imperative to act. Admittedly, there is room for limited moral determinations when a state invokes the inherent right of self-defense. This aside, the Charter makes no room for subjective state action and disallows any aggressive use of force. This prohibition is absolute as a deviation from the Charter’s methodology, for any reason, invites a return to the era of discretionary warfare.

To those frustrated with the Syrian atrocities, the inability to legally justify an intervention under the traditional use of force construct is an unconscionable result. This may seem especially true given the repeated failures of the United Nations to act in Syria. Circumventing the United Nations Charter, in this circumstance, may seem like the moral or right thing to do. But it is important to ask what poses a greater risk to international peace and security: a morally repugnant act left unaddressed or empowering nations to unilaterally initiate war at will? We know how the drafters of the United Nations answered this question. Perhaps we should not be so quick to ignore their wisdom.