[XorNot]

> What about if you're doing something that isn't illegal yet, but a new Politician decides he doesn't like the cut of your hair and then targets you later because you were doing it.

That would have nothing to do with parallel construction and everything to do with someone having sufficient political power to change the law to target you - either specifically or generally.

Someone with that much power could also just wipe out illegal search and seizure restrictions.

But again this is also based on a misunderstanding of the process: you can't use parallel construction to make illegally obtained evidence valid to use. You can only use it to indirectly guide the discovery of other evidence which must already exist and be plausibly findable by regular means.

i.e. if the police stop on the high way and notice disturbed ground and discover a dead body, that's something which could happen by pure chance. Parallel construction is suggesting that a police car should stop at a particular point on a highway, and have a good look around.