A U.S. drone strike has reportedly killed a leading cleric of al-Qaeda’s branch in Yemen. A religious theologian, Ibrahim al-Rubaysh had risen to the level of top cleric or Mufti within al Qaeda in the Arabian Peninsula (AQAP). He would not be the first al-Qaeda affiliated Mufti to be killed by U.S. forces. In June 2005, U.S. military troops in Iraq reportedly killed the cleric Abdullah al-Rashoud. But in that case, it appeared that the cleric may have been incidentally killed during heated battles (Operation Spear).

The initial reports of the death of al-Rubaysh do not state whether he was the target of the alleged U.S. drone strike. If he was, a key legal and moral question that major media outlets (AP, NYT, etc.) are not asking: is a cleric like al-Rubaysh a legitimate military target?

The law of armed conflict permits the targeting of members of armed forces and civilians who directly participate in hostilities. As a general matter, religious leaders are simply not lawful targets. For example, the International Committee of the Red Cross states: “Members of State armed forces (except medical and religious personnel) or organized armed groups are generally regarded as legitimate military targets.” But the ICRC guidance also notes: “medical and religious personnel of the armed forces lose their protection in case of ‘hostile’ or ‘harmful’ acts outside their privileged function.” For example, military chaplains – who are members of armed forces – could lose their legal immunity from attack if they participate in hostilities.

A question then is what activities by a religious leader could constitute such participation. What if al-Rubaysh was involved in approving (i.e., religiously sanctioning) military operations and targets? In an analysis of al-Rubaysh, the Long War Journal states: “The role of Mufti is crucial for al Qaeda’s operations because the Mufti provides the theological justifications for the organization’s terrorism.” And the Department of State notification of a $5 million reward for information leading to al-Rubaysh’s location described him as “a senior AQAP Sharia official and advisor who provides the justification for the group’s attacks and participates in attack planning.”

To be sure, the second element in the State Department’s description – “participates in attack planning” — might be doing all the work for why al-Rubaysh was killed. That is, perhaps al-Rubaysh had a secondary role in which he directly “participate[d] in attack planning” in the form of more traditional military advice and decision-making. The State Department’s December 2014 designation of al-Rubaysh as a Specially Designated Global Terrorist also described him as a “senior advisor for AQAP operational planning and is involved in the planning of attacks.” In that case, the US could have targeted him “in spite of” and not “because of” his clerical role. I am dubious about this line of reasoning. The public record suggests that al-Rubaysh was a theologian and his reported activities on behalf of AQAP as a spokesperson and ideologue fit that description. His participation in “attack planning” would presumably have been on the basis of the same function in the group – that is, providing ethical and religious guidance. (Note to the Obama administration: here’s where transparency would be important.)

So what does international law say about whether religious advice in attack planning could make an individual a lawful military target?

A background paper from proceedings organized by the ICRC suggests that this is an issue over which international legal experts might be divided:

Religious leaders deciding on the basic engagement of their armed forces and groups were considered to be engaging in DPH by only 6 experts (against 7 “no” and 6 “n/a”), and decisions by religious leaders on specific methods to be used by their forces were considered to constitute DPH by 7 experts (against 6 “no” and 6 “n/a” respectively). Decisions of religious leaders on specific operations and targets were clearly found to constitute DPH by 10 experts (4 “no”; 5 n/a).

If the US did, in fact, target al-Rubaysh on the basis of his religious role, some will consider the division of expert opinion favorable for the United States action, and others will draw the opposite conclusion. The supporters might say: “see, it isn’t clearly unlawful and reasonable minds can disagree.” The critics might say: “see, it is highly controversial and no clear majority of international law experts would support it.”

Decisions made on the battlefield with AQAP do not stop there. Where we draw the line on killing religious leaders at this time has implications for the laws of war and military operations more generally and into the future.

So, where should one draw the line morally as well as legally? If a cleric is directly involved in justifying particular operations and endorsing target selections, isn’t that person equivalent to military planners in the process? On the other hand, isn’t that the very sort of advice that religious personnel in armed forces provide to military commanders and the troops as part of their common (and legally privileged) function? Perhaps the difference lies in the level of authority – whether the individual has the power to call off particular operations and particular tactics?

At the very least, it is important to know on what basis the US targeted al-Rubaysh and, depending on the answer, these second-order questions about targeting clerics may need to be squarely addressed.