This might seem an odd question but follow me on this…
It’s a given in British constitutional law that the Prime Minister cannot be a Roman-Catholic even though nowhere is there a specific injunction in law to this effect.
The reason for this derives from the fact that within the British constitution the Prime Minister wield the ‘royal prerogative’ - a set of powers, including the power to appoint Ministers, declare war and a few other things besides that, strictly speaking, belong to the Crown - in effect in wielding the royal prerogative the PM is acting directly in lieu of the Monarch and subject to the same strictures imposed in law as would otherwise apply to the Monarch, notably those derived from the 1701 Act of Settlement, which is the Act of Parliament which prevents a Catholic from ascending to the throne.
Now…
What the 1701 Act of Settlement actually says is:
“And it was thereby further enacted, that all and every person and persons that then were, or afterwards should be reconciled to, or shall hold communion with the see or Church of Rome, or should profess the popish religion, or marry a papist, should be excluded, and are by that Act made for ever incapable to inherit, possess, or enjoy the Crown and government of this realm, and Ireland, and the dominions thereunto belonging, or any part of the same, or to have, use, or exercise any regal power, authority, or jurisdiction within the same:”
Which is pretty unequivocal, if you ask me.
The key points here are that the prohibition on Catholics in the Act of Settlement extends not only Catholics, themselves, but to anyone who marries a Catholic as well - Cherie, of course, being a Catholic - and that amongst the various things that a Catholic (or someone married to one) cannot do is “exercise any regal power, authority, or jurisdiction” - i.e. the royal prerogative.
So, on that basis, it looks very much a possibility that Blair may not legally be the PM, or at least he may not legally be permitted to make use of the royal prerogative, which would make every government appointed by him since 1997 illegal, as well as the war in Iraq and a whole shitload of other things besides.
One for the constitutional lawyers, methinks.



