Tony Blair’s decision in 2003 to ask parliament to approve his decision to join the invasion of Iraq created the convention that MPs be given a say over use use of force. The convention also forced David Cameron to ask MPs to vote on whether or not to support his call for military action against Syria earlier this year – a vote he unexpectedly lost.
However the power to deploy the military still rests in the hands of the prime minister and there is no legal requirement for him or her to ask parliament for permission.
In March 2011, as MPs debate the deployment of British forces over Libya, William Hague told the Commons the government intended to change this ancient power: “We will also enshrine in law for the future the necessity of consulting Parliament on military action.”
However appearing before the Commons constitution committee today, Lib Dem Cabinet Office minister Lord Wallace of Saltaire indicated the government had changed its mind.