With western support for military intervention in Syria growing, what options are open to states such as Britain, France and the US as they try to legitimise military action?
The European Union has consistently argued for the importance of UN Security Council support. But Russia's and China's vociferous opposition to military intervention against the Assad regime means that a security council mandate is highly unlikely.
The suggestion by Britain and the US in recent days that they are willing to bypass the council signalled a significant, if unsurprising, shift. Indeed many western powers have long argued that it is irresponsible to insist that military intervention should be dependent on security council support, as this gives an effective veto to countries such as Russia over matters relating to international affairs.
Military intervention without security council support is not unprecedented – the Kosovo war in the late 1990s went ahead without its backing, for example. Russia supported Serbia during the conflict.
Attention is also turning to the role of Nato. The organisation has generally been reluctant to involve itself in conflicts outside the North Atlantic area. In an interview with The Irish Times in February, Nato general secretary Anders Fogh Rasmussen dismissed the notion of intervention in Syria.
"Nato can't be the world's policeman who travels from country to country to solve crises. That's not possible, but as we saw in Libya, we can take action if needed, for instance to fulfil a United Nations mandate. We did so successfully, we prevented a massacre on the Libyan people. But in other cases there may be different conditions, a different situation, and in those specific cases we conclude that a military solution is not the right way forward Syria is an example."
While Nato has since reiterated this stance, reports of chemical attacks are likely to have changed the terms of the debate. Contacted by The Irish Times yesterday, a Nato official said the organisation was "keeping the situation under review", but said the allies of the 28-member organisation were "deeply concerned by mounting evidence of the use of chemical weapons in Syria".
“The use of chemical weapons is completely unacceptable and a clear breach of international law,” he added.
Nato ambassadors are scheduled to meet this week in Brussels. Unlike with the UN Security Council, all decisions by Nato are made through consensus. With Russia and China out of the picture – neither is a member of the organisation – support could be forthcoming, with countries such as Germany that have previously been against intervention appearing to soften their stance in recent days.
Another source of legitimacy for the western powers may be, if established, the Syrian government's deployment of chemical weapons, which could be classed as a crime against humanity, while Syria's neighbouring countries, such as Israel and Turkey, could also claim the right to self-defence under the UN charter. The principle of "responsibility to protect", which emerged from the Kosovo and Rwandan wars in the 1990s, which obliges the international community to protect populations under threat, may also offer legal justification for action.
Perhaps the biggest challenge for the western powers as they move closer to military intervention will be a lack of support from their own citizens. The British public, still scarred from the deeply unpopular Iraq war, is wary of being dragged into another Middle East conflict.
Already shadow foreign secretary Douglas Alexander has demanded that the British government set out the legal case for intervention. As MPs cut short their summer break and return to Westminster to debate the issue, expect some tough questions and answers in the House of Commons.