Re: Arbitrary law is reappearing
The UK Supreme Court does not do any such thing. It rules on whether actions are legally permitted by existing UK law - primary, secondary and precedent.
Remember that Parliament makes laws, not Government. And so when Government breaks the law, they must be held to account. And when Parliament makes laws, they must be compatible with existing law.
If a new law is incompatible with an existing one, Parliament must explicitly remove the old one. The Lords are supposed to try to spot these before the Act is enacted, however that can't deal with secondary legislation or government overreach.
That seems to be what you claim to want - except of course "violates your ethics" is the most subjective view possible, so presumably you do think the PM should be allowed to do whatever he or she desires, regardless of what laws Parliament has created.
If your existence violates my sense of ethics, should I be permitted to terminate it? Of course not.