Last night’s parliamentary vote against military action in Syria was constitutionally significant. The UK is said to have an ‘unwritten constitution’. There is no single document called ‘The Constitution’. Instead the constitutional fabric of the country is made up of conventions, documents, and individual pieces of law. Which laws have constitutional significance is up for debate, but they would certainly include the Reform Acts of the 19th century, the 1928 Equal Franchise Act, the 1976 Race Relations Act and the 1998 Human Rights Act. The Cabinet Office Manual first published in 2010 is not a law but is in effect a constitutional document stating how government should work. Conventions are less tangible but no less significant. The Salisbury convention is that the House of Lords will not vote down government bills mentioned in an election manifesto. The ‘Royal Prerogative’ is another and was challenged in parliament last night. Royal prerogatives are traditional powers of the sovereign that have been passed to the executive. The ‘Royal Prerogative’ in the singular refers to the power of the Prime Minister to wage war. Hence no PM has ever needed to consult parliament to deploy the military.
Last night’s vote was the culmination of ten years of constitutional change. In the run up to the Iraq war, many politicians pushed hard for parliament to have a say. The gravestone of Robin Cook reads: ‘I may not have succeeded in halting the war, but I did secure the right of Parliament to decide on war.’ Prime Minsters after Tony Blair have promised that parliament would have a vote on military action. This began to establish a constitutional convention, but last night cemented it. Parliament has voted on military action before, over Libya for example, but yesterday was the first time it has rejected a Prime Minister’s military policy. Parliament has now demonstrated that its vote will not simply be a rubber-stamping exercise in deference to the constitutional authority of the Prime Minister. True, a future PM could technically bypass parliament on military action, because nowhere is it written down that there must be a vote. But that has now become unthinkable. Being unthinkable is one of the most important constitutional safeguards the UK has against the unthinkable, such as parliament abolishing female suffrage. And true, a future PM without a hung parliament could be more sure of winning. But that’s politics. This is the establishment of a constitutional convention.