Photo: A U.S.-made Saudi F-15. Image: Meteb Ali via Wikimedia Commons.

This is piece is the latest article in our forum on the Yemen crisis and the law.

Under international law, a non-international armed conflict, or NIAC, exists where there is “protracted armed violence between governmental authorities and organized armed groups or between such groups within a State.” If applied to Yemen, this test reveals that there are a number of NIACs currently under way in Yemen:  First, there is a NIAC between the government of Yemen and the Houthis.  Second, there are NIACs between the United States and the Islamic State, al Qaeda, and AQAP—groups that the United States is directly targeting in counter-terrorism air and ground operations.  Third, there are NIACs between non-state actor groups within Yemen (for example, between the Houthis and the Islamic State). Fourth, there are NIACs between the states that make up the Saudi-led coalition and the Houthis.

The more difficult question is whether the United States is a party to the NIAC between the states in the Saudi-led coalition and the Houthis. The intensity of fighting between the United States and the Houthis is not, at present, sufficient on its own to meet the intensity threshold to qualify as a NIAC.  (The only direct exchange of fire publicly reported is the exchange between the U.S. Navy ships and Houthis in October 2016, but that was limited and appears unlikely to resume. If that were to change, then the legal analysis would, of course, change as well.)

However, the International Committee of the Red Cross (ICRC) has argued that that a third-party state or multinational coalition supporting one side in a NIAC does not need to meet the same intensity threshold in order to be a party to the NIAC. It explained: “[I]t is not always necessary to assess whether, on their own, the actions of multinational forces meet the level of intensity required for the existence of a new non-international armed conflict in order for them to become Parties to that conflict.”  It noted that this may be the case when, for example, “multinational forces are already involved in a non-international armed conflict against a non-State armed group and additional foreign forces provide support to the multinational forces.” In such cases, “depending on the function(s) they fulfil, the States sending such forces may also become parties to the non-international armed conflict.” The ICRC notes, moreover, that “[t]he decisive element would be the contribution such forces make to the collective conduct of hostilities. Only activities that have a direct impact on the opposing Party’s ability to carry out military operations would turn multinational forces into a Party to a pre-existing non-international armed conflict.”

Some argue that the deployment of forces is not necessary for a state to join a pre-existing NIAC. Nathalie Weizmann, for instance, describes a four-part test whereby a supporting state becomes party to a “pre-existing NIAC” if it “undertake[s] actions related to the conduct of hostilities,” “in support of a party to that conflict” and “pursuant to an officialdecision” by the supporting party. The ICRC’s Legal Adviser Tristan Ferraro and others have likewise argued that “providing planes for refueling jet fighters involved in aerial operations carried out by the supported state,” as the United States has done for the Saudi-led coalition, might implicate the states as a party to a pre-existing NIAC.

As yet, with the exception of a very small number of personnel operating outside the theater providing some logistical support, the United States has not sent forces to support the Saudi-led multinational coalition. It has therefore had relatively little direct effect on the Houthis’ ability to carry out military operations. Nonetheless U.S. support for the Saudi-led coalition has been described as essential. Given the more lenient test applicable to parties joining a pre-existing NIAC, it is possible that such support is sufficient involve the U.S. in the NIAC between those states and the Houthis despite the U.S.’s lack of any significant direct participation.  Applying the test proposed by Weizmann, for example, the United States has undertaken actions related to the conduct of hostilities (refueling, provision of munitions, etc.) in support of a party to that conflict (the states that are in the Saudi-led coalition), pursuant to an official decision by the United States government.

In the end, it is worth noting that, at the moment, relatively little turns on the conclusion that the U.S. is or is not party to the NIAC between the Saudi-led coalition states and the Houthis.  As long as the United States is not using direct force against the Houthis, its legal obligations are the same whether or not it is a party to that particular NIAC. If the United States were to use force against the Houthis, however, the lower threshold for triggering participation in a pre-existing NIAC could be important to shaping the U.S.’s legal obligations. In that case, it would be appropriate for the United States to proceed under the assumption that the legal obligations attending to a party to the conflict apply to its actions, even if the intensity threshold might not have been met if the events were analyzed in isolation.