In the ongoing debate over the use of lethal force against persons located outside Afghanistan, the suggestion is often made (both by supporters and critics of US government policies) that Afghanistan is a "hot battlefield" whereas places like Yemen are not. But this is not accurate. Separate and apart from whether there is a single, borderless armed conflict between the United States and al Qaeda, there certainly are circumstances of armed conflict in Yemen. Consider the following excerpt from this ABC report:
The military officials accounts of the disaster involved al-Qaida militants sneaking across the desert to the back lines of Yemeni forces at dawn, when many of the troops were asleep in their tents.
The raiders sprayed the sleeping soldiers with bullets and later dumped their bodies, including some missing heads or mutilated, in the desert near Abyan's provincial capital of Zinjibar.
On Tuesday, military officials said the death toll among army troops has risen to 185. Another 55 soldiers were captured and paraded through a nearby town by the militants. The figure for al-Qaida fighters killed in the fighting remained unchanged at 32.
Medical officials in the area confirmed the latest death toll and said some of the bodies of soldiers recovered were missing their heads and bore multiple stab wounds. They said that bodies packed the military hospital morgue to which they were taken, with some taken to vegetable freezers in a military compound for lack of space.
The military officials had earlier said that militants overran the base and captured armored vehicles and artillery pieces, which they turned on the army.
I don't think there is any serious doubt that Yemen has a NIAC underway within its borders. It is indeed a "hot battlefield," at least for purposes of the Yemeni government. The interesting question, though, is whether this observation is relevant with respect to the use of lethal force by the United States in that same location.
On this view, the real difference between Afghanistan and Yemen is not whether one or the other is a combat zone. Both are. But we have an overt combat deployment only in the former location, whereas in the latter our involvement appears limited to relatively episodic uses of lethal force, on a covert or a clandestine basis, by both CIA and JSOC (and perhaps other non-SOF military units, as with occasional airstrikes by manned aircraft and missile strikes presumably launched by the Navy). This factual distinction matters in the sense that it is very easy to make the case that the United States is party to a relevant NIAC when it uses force in Afghanistan, precisely because of a large-scale and highly-visible role there, whereas it is murkier whether the same is true in Yemen. For my part, I think the scale, nature, and intensity of US involvement in Yemen is sufficient to make us party to that NIAC, alongside the Yemeni-government. If that is correct, then the question whether there is also a globe-spanning NIAC with al Qaeda (and the related question whether AQAP is sufficiently linked to AQ) need not be answered in order to come to the conclusion that LOAC applies to those attacks.
Would one still need to make a determination on the AQAP-AQ relationship, and the notion of a borderless conflict with AQ, for domestic law purposes? That is, would those questions still be central to the determination of whether the government has authority to use force in Yemen? Yes, if the only basis for domestic authorization is the 9/18/01 AUMF. But the answer is no if you believe that AQAP's own conduct, in attempting on multiple occasions to carry out bombings of US-bound airplanes, implicates the President's Article II authority (and responsibility) to use at least some degree of military force on a defensive basis (ala the Clinton Administration's use of cruise missiles against al Qaeda in 1998, shortly after the East African embassy bombings, as well as earlier Reagan administration actions in relation to Libya).