As I understand it, it is quite possible to do this within the rule of law. To avoid the monarch refusing to enact this, it would need to be done in two stages:
1. A new Royal Assent Act, that makes assent automatic upon a bill passing both Houses. Assuming this in itself receives assent, it would remove the monarch's power to veto or refuse a bill (a power that hasn't been used for over 300 years anyway).
2. A Republic Act, that transfers all powers, abolishes the monarchy, strips them of their wealth, exiles them, etc.
The underlying assumption of the parent commenter is that “rule of law” means something other than 50%+1 of the House of Commons voting something into effect.
For instance, if parliament passed a law allowing “The Purge” to happen yearly, would murders committed on that day be “rule of law”? If you don’t think so, perhaps you agree there are some inherent principles to rule of law that aren’t simply a majority vote of a legislature. (For instance, perhaps there’s an assumption that exiling someone who hasn’t committed any crime is a violation of due process rights, rights as a citizen of the country, etc.)
This is the major question that liberalism tries to solve. This is why in a liberal democracy, minority protection all the way to the individual is a top priority -- the 51% are not allowed to do anything they want.
I think what the other commenter was trying to say was not that it would be impossible to do so, but that it would not be "right", so to speak.
While you could of course exile them like other countries have done in the past, why would you do that? What reasoning would you use to justify exiling them, striping them of their personal property etc. ?
Abolishing the monarchy is one thing, it can be justified pretty easily, the interests of the people. Anything beyond that however would be punishment, what have they done that is currently illegal that warrants that punishment? Punishing them simply "because they are royals" doesn't really work out, that isn't illegal after all.
Technically just abolishing the monarchy / taking away their powers would suffice.
It wouldn't have to be deemed a punishment, merely a procedural item as part of establishing the Republic of Britain and eradicating any trace of royal privilege.
> Technically just abolishing the monarchy / taking away their powers would suffice.
It wouldn't suffice, because they still derive a great deal of power from their inherited wealth. What's the point of abolishing the monarchy if we permit them to remain as landlords for huge swathes of the country? Then they're still lording it over people economically, even if no longer doing so constitutionally.
I hope you'll excuse me for phrasing it this way, but it would not be a punishment only because a punishment is a lawful injury, and your "Republic Act" is decidedly unlawful: by interfering with the royals' persons, property, privacy, &c, without any clear finding of wrong-doing on their part, the act is offensive to the common law, the ECHR law, and other fancy international law. (Good legal scholarship has shown us in recent years that most of the ideas in the ECHR and other international conventions are derived from the English common law, a rich tradition of which you should be proud.)
I am no fan of the royals and other nobles and look forward to the day when they all work for a living and wear seat belts like regular people. Yet, we must acknowledge that rule of law means law for the bad, the useless, and the rich. The ends don't justify the means.
Sometimes, what you're describing is called "rule by law" to distinguish it from "rule of law", because one practical aspect of rule of law is that everyone is subject to the law, even lawmakers.
This is not an intuitive concept by any means, but it helps to think about it in terms of the origins of the common law: the underlying idea is that the long acceptance of something or practice of something by regular people is a sound basis for its legitimacy. This still finds expression in the theory (in the US, anyways) that the speed limit should be the speed at which 85% of people drive. On this footing, the legitimacy of law is more about observation than about the decision of a particular person or administrative body.
Some things to contrast with the common law are "positive law" and "statute law". Legislation passed by Parliament is indeed statute law; it's not common law. Yet, to a significant degree, common law ideas and ways of judging remain prevalent in the United States, the United Kingdom and the other English speaking countries. It's the common law that defines most crimes with which you'd be familiar. It's more relevant than you think.
Although Parliament is indeed sovereign and Parliamentary sovereignty is said to mean that Parliament can not be bound even by Parliament, there are contemporary limits recognized to Parliament's law making authority. Sometimes they are even called "constitutional", referencing the unwritten English constitution; and sometimes they are clearly linked to the Convention on Human Rights. Either way, what we see here is an assertion of the old idea of "transcendent law" that binds everyone, even the law makers -- and that is what rule of law is really about.
1. A new Royal Assent Act, that makes assent automatic upon a bill passing both Houses. Assuming this in itself receives assent, it would remove the monarch's power to veto or refuse a bill (a power that hasn't been used for over 300 years anyway).
2. A Republic Act, that transfers all powers, abolishes the monarchy, strips them of their wealth, exiles them, etc.
Where is the debasement here?