[growse]

> No, it would not be illegal to make a law whose punishment was an oubliette. The British Parliament is sovereign and supreme, and can make any law it wishes.

Sure, but this is the same argument that comes around whenever previously signed treaties become 'inconvenient'.

Parliament can, of course, choose to ignore EHCR/Geneva/pick-any-other-ratified-treaty. But there are both predictable and unpredictable consequences for doing so, so in practice it's prudent for parliament to not just wield their unlimited power to just start murdering whoever they fancy.

[matthewheath]

I think prudence really depends on the whim of the executive, since generally the executive is Parliament given the majority it normally possesses. A number of British governments have historically shown little regard for the unpredictable consequences of violating international law.

For example, Iraq, the Chagos Islands, the Brexit trade deal concerning customs checks in Northern Ireland, etc.

I suppose it's all really just one big political matter: do they want to chance it? Probably not, but they could, legally. We just haven't had the government who's willing to do that yet, but given the current government's willingness to flout international law, prudence seems like it might have vanished some time ago...