On Friday, the British House of Commons overwhelmingly voted (524-43) to approve the U.K.’s participation in airstrikes against ISIL targets in Iraq. The success of the vote was largely predicted after Prime Minister David Cameron reached an agreement with Opposition Leader Ed Miliband on the motion, but the nearly seven-hour debate (full text) contained notes of skepticism and caution. Several members of parliament questioned the lack of a broader strategy to tackle ISIL or the underlying problems in the region, and whether the Iraqi army has the ability to defend against ISIL on the ground.

In this post I wish to highlight the arguments that were made in relation to the legality of extending British military action to neighboring Syria. The motion specifically ruled out strikes in Syria, but the Prime Minister laid the groundwork for such an extension early on in the debate. While Cameron acknowledged that “the Syrian situation is more complicated than the Iraqi situation,” he said he did not believe there was a legal barrier to action in Syria. Cameron cited two reasons. First:

“In this [Iraq] case it could not be clearer that we are acting at the request of a sovereign state, and if we were to act in Syria, I believe that would be the legal basis too: collective self-defense against ISIL which threatens Iraq.”

Second, Cameron pointed to the need for possibly averting a humanitarian catastrophe. On this point, Cameron left open the possibility of urgent action in Syria without consulting parliament:

“Let me be clear again … if there was a moment when it looked as though there could be an urgent humanitarian need for intervention, I would be prepared to order that intervention and then come to the House and explain why.”

The recently replaced Attorney General, Dominic Grieve, agreed that action could be pursued in Syria on the basis of collective self-defense of Iraq and the doctrine of humanitarian necessity—“even if no [Security Council] resolution is present.”

Opposition leader Ed Miliband, on the other hand, would prefer to seek UN Security Council approval before supporting military action in Syria. On the Syria question, Miliband said:

“First of all, there is the question of legitimacy. There is a strong argument about the legal base for action in Syria under article 51 [of the UN Charter]. The point that I have been making in the last few days is that, in my view, when we are not talking about being invited in by a democratic state, it would be better—I put it no higher than that—to seek a UN Security Council resolution.”

The shadow foreign secretary, Douglas Alexander, sought to clarify that a Security Council resolution on Syria was not a precondition to future Labour party support, but stated that “[g]iven the controversy that has surrounded international action in Syria in recent years, we think that any actions that can secure broader legitimacy would assist in the completion of that mission.”

Several members of the House cited the non-existent border between Iraq and Syria as a reason to pursue military action against ISIL across the border, without providing further legal analysis. Some questioned the likelihood of obtaining a Security Council resolution on the issue, given the expected Russia veto. And some others (including the Opposition Leader) warned against the outstanding question of a credible ground force in Syria with which to ally, as well as the lack of an overall strategy in Syria (with the Assad regime proving an especially complicating factor).

Interestingly, no member of the Commons referred specifically to the relatively controversial “unwilling or unable” test—cited by the U.S. in its letter to the UN pursuant to Article 51—as a possible legal justification. However, in a parallel debate in the House of Lords, one member, Lord Hannay, specifically relied on the Assad regime seeming to be “both unwilling and unable to do anything to” prevent the attacks launched against Iraq from areas in eastern Syria under ISIL control, “which is assuredly [Syria’s] duty under international law.”

A final point worth highlighting is the statement of Dai Havard, who led a recent report of the Commons Defense Select Committee on the legal framework for military personnel in future operations. Havard offers the following warning on the practical difficulties of extending operations to Syria:

“If an aeroplane were to go down in Iraq, the search and rescue mission would not be a problem; should an aeroplane go down in Syria, there could well be a problem. There is this “hot pursuit” argument being made, that if Iraq is now defending itself, it is therefore legitimate for it to go over the border into Syria to do so, and to be supported by the Americans and others. However, do we all of a sudden vicariously gain legal legitimacy because we are part of the support activity for that process? Where would that situation leave individual members of the military in terms of their legal certainty?The issue of protection is equally as important for the individual as it is for the collective approach that we are taking.

Given the discussion that took place on Friday—and particularly taking into account statements of the political leaders—it seems as though it will only be a matter of time before the question of strikes against ISIL in Syria will be pursued by the government, although whether it will choose to consult parliament appears less clear. However, the looming general election (May 2015) combined with last year’s unsuccessful Syria vote may be reason enough to obtain parliament’s approval before going into Syria.