There are various Acts of Parliament for "constitutional" matters, such as the Parliament Acts and Human Rights Act, but in theory they can be amended or abolished at any time by a simple majority in Parliament. The underlying constitution is built on common law, unwritten custom and precedent. If an important precedent is laid down, later governments ignore it at their peril.
One of the very few good aspects of the Iraq War was that before it started, Tony Blair held a vote in the House of Commons to authorise a declaration of war. In the past, Prime Ministers had declared war under royal prerogative without consulting Parliament; for example, this was done by Margaret Thatcher at the start of the the Falklands War. In theory, Blair could have done the same thing, but the Iraq War was so controversial that he wanted the political cover of endorsement by MPs.
The Commons vote on military action in Syria in 2013 reinforced this precedent. David Cameron was a supporter of airstrikes in Syria, but his government lost the vote, so plans for military action were shelved. A good discussion of the wider legal issues is here.
|The Palace of Westminster, home of the UK Parliament.
The Scottish referendum has established another important precedent: If a majority of the Scottish Parliament in Holyrood votes to hold a referendum on independence, the Westminster government will cooperate and abide by the result.
If there is a Yes vote on 18 September, Scotland will declare independence and this becomes a moot point. But if there is a No vote and Scotland remains within the UK, Holyrood will retain the option of holding another independence referendum.
After a No vote, the powers and funding of the Scottish Parliament would not stand still:
- Additional powers for Holyrood are already being implemented under the Scotland Act 2013.
- The main UK political parties have promised further devolution of power following a No vote, over and above the 2013 Act, although as yet details are limited and there is no consensus between the parties.
- Last but not least, the Barnett formula which determines the size of Scotland's grant from the UK Treasury could be subject to review at some future date.
|The Scottish Parliament building.
In the event of a No vote, time will tell whether Scotland decides to vote again on independence. In Canada, Quebec said no to independence in 1980 and much more narrowly in 1995. It may be that Scotland reaches a new devolution settlement, which brings general acceptance for remaining within the UK; or grievances may build up to the point where another referendum is called.
At the very least, the referendum precedent will deter the Westminster Parliament from imposing deeply unpopular measures on Scotland. There is unlikely to be a repeat of the poll tax from the 1980s.
Scotland is a distinct nation within the UK, with the potential to go it alone as an independent entity. The very existence of the independence referendum has made this clear. Even if Scotland votes No on 18 September, by creating this precedent the SNP has done Scotland an important service.