It is quite wrong to say that Mrs. May is seeking to use what some call “archaic Royal Prerogative powers” to trigger “EU exit.”
First, Article 50 of the Lisbon Treaty is starting a negotiating process, not the EU-UK Treaty itself. When its provisions are agreed by the negotiating parties, each of the 28 states will have to ratify it for it to come into force. This will not happen automatically. Probably all 28 countries will have to embody some at least of its provisions in their own Law. This will be done in our own Law via the mechanism of one or more Acts of Parliament. These will be fully debated, as the Maastricht Treaty setting up the Single Market was in 1992.
Second, “Royal Prerogative” is just a fancy phrase for the government itself. No government either at home or abroad has ever held itself bound by its Parliament during the course of negotiating a treaty with a foreign power, not Edward Heath when negotiating the EU Treaty of Accession in 1972, nor more tellingly did Attlee, when his foreign secretary Ernest Bevin negotiated the NATO Treaty with the US and Canada virtually in secret. This had and continues to have huge implications for the defence and duties of UK citizens.
In 1975, the late Norris McWhirter (of the Guinness Book of Records) and his brother appealed to the High Court to have the Referendum result (keeping Britain In the EEC) held pending a definitive vote in Parliament. His appeal was struck out as having “No merit” without even being heard. The same should have been done to the current Miller application, but of course the judges are not at all personally independent in the matter of Britain’s membership of the EU, either in 1975 or now.
The matter is intensely political: no rights are being taken from anyone by triggering Article 50 of the Lisbon Treaty. This is an elected government matter, mandated ironically by the same Treaty signed by the British Prime Minister (Gordon Brown) using, guess what, the same “Royal Prerogative”. For the High Court or Supreme Court to pretend otherwise is patently absurd.
To test the veracity of this statement, does anyone really believe that the Courts would require the UK Parliament to approve negotiations starting on Scottish separation if a referendum in Scotland had approved this, even though an overwhelming majority in the House of Commons would oppose it. The implications for the rest of the United Kingdom would be far greater than merely losing highly marginal and largely unwanted rights such as the right to vote for the European Parliament?
With all this though, Britain should have a proper written constitution, approved by the people in a referendum (see the British Constitution page of this website).