Two further thoughts on the Convention governing resignation of the Prime Minister.
First, what happens in practice if, come May 8th, the result is unclear? What if Con + Lib Dem + DUP is at 320 (majority is 323 = 650-5 Sinn Fein/2), and the Conservatives manage to get the agreement of the Lib Dems and DUP to support them. In such a finely balanced case (with possible Ukip MPs, and Independents), I think the proper course is for confidence to be tested in a vote. Put another way, we return to the 1920s and Cameron would be acting correctly (or at least within the Convention) not to resign immediately, and require the issue to be tested in Parliament.
The last time this happened was in 1924. Baldwin was Prime Minister going into the election in 1923. The Conservative party had a plurality of seats but was well short of a majority. Upon reconvening, the House debated a vote of no confidence, which was passed, causing Baldwin to immediately resign, advising the King to call on MacDonald.
Here are the proceedings in Hansard.
MacDonald’s government only lasted until October, when defeat in another General Election led to the return of Baldwin.
Let us hope all 645 are in robust health.
Second, how may Conventions be changed by legislation? A Constitutional Convention confines how a legal power or discretion may be exercised. So, the sovereign, as a matter of law, has a great deal of discretion in how he or she exercises the powers of appointment and dismissal of a Prime Minister. Constitutional Convention means that, in practice, the sovereign has no such discretion.
This means that a Constitutional Convention relates to a discretion that a person with authority (the Sovereign, the Prime Minister, the House of Lords etc) has , and restricts the wider scope that it has as a matter of law. A statute may amend or remove a Convention not by directly changing it (it cannot do that, because Conventions are definitionally not matters of positive law) but by changing the legal rule to which the Convention relates. There are not, to my knowledge, statutes of the form “the Constitutional Convention to do X is hereby abolished.”
By Convention, members of the Judicial Committee of the House of Lords did not vote in matters of political controversy. In 2005 the Constitutional Reform Act removed them from Parliament. The Convention came to an end because the power to which it related came to an end.
By the Ponsonby Convention, international treaties had to be laid before Parliament 21 days before ratification. The Constitutional Reform and Governance Act 2010 laid down rules requiring treaties to be laid before Parliament 21 days before ratification, removing the Crown’s power to do otherwise, thereby abolishing the scope for any Convention on the matter.
If we look at the Fixed Term Parliaments Act, what does it do? Prior to the Act the PM could call on the sovereign to dissolve Parliament, and by Convention she always acceded. The Act removes the power to dissolve Parliament save in accordance with its terms, and so that Convention falls with it.
The Prime Minister also has a discretion whether to resign, and instruct the sovereign to call on someone else to form a government. Assuming this power to be constrained by Convention (as it is), does the Act say anything about the legal power to which this Convention relates?
[I am grateful to Professor Gavin Philllipson for making me think about the Ponsonby example. The views above are mine alone.]