The United States and United Kingdom have carried out a series of strikes upon Yemeni territory since January 2024. The acting States have justified these on the basis of the right of self-defence in response to the series of attacks that have been perpetrated by the Houthi group in Yemen against various commercial and military vessels in the Red Sea. On the face of it this was a relatively straightforward justification. Yet, when subjected to analysis it becomes evident that not only is the justification itself not clear, but that the law governing the actions—the jus ad bellum—is not sufficiently settled to provide clear parameters by which to assess the legality of the strikes. Furthermore, the strikes themselves, and the purposes for which they were undertaken, may have set a precedent with unforeseeable consequences.