The problem with that view is that when the "strong legal basis" is not codified, and codified in a way that nonspecialists can at least vaguely identify and understand, it gets a lot easier to get away with ignoring it. Which the UK has been going hog wild doing in the last 20 years or so.

I am not saying the US is better in practice. The bottom line is that authority worshippers will take whatever liberties they can get away with in any system.