I think “according to the law” is doing a lot of heavy lifting. That is the part that really makes it an oath to the ‘constitution’ of the UK. You are pledging alligence to the figurehead of the government, to obey them/the government, as long as they/the government are acting legally. If the government does something illegal, or asks you to do something illegal, you should not obey them.

I’m British, and not a fan of the monarchy (especially Charles) but I think that we can see the advantages of having a head of state who has very little power to fuck things up, and that isn’t a position that outside forces billionaires can buy their way into, but has the power to remove a Prime Minister if they tried to do something unconstitutional.

The idea of checks and balances in the US didn’t seem to plan for a bad president being elected with enough support in the house and Senate that he becomes pretty much untouchable (especially after a first term stacking the SC).