Michael Schmitt and Christopher Ford unpack the Trump Administration’s legal justifications for the April 2017 United States attack on a Syrian airfield in response to its use of chemical weapons against civilians. Schmitt and Ford discuss three possible legal bases for the use of force: self-defense, response to an internationally wrongful act, and humanitarian intervention. The authors conclude that the US’s actions run afoul of limitations in each relevant body of law, and of note, they discuss how this attack is consequential for the validity of humanitarian intervention on another state’s territory without approval from the UN Security Council. They conclude by suggesting that the international community is likely to consider the nature of suffering, in addition to the quantum of suffering, as bearing on the right of States to mount future humanitarian operations.