Let's say someone illegally parks in a handicapped spot, and you witness it. Perhaps you tell them it's wrong, and they refuse to move.
Let's recognize that some people are handicapped and it's not clearly visible; but in that case the vehicle should have a placard. There's common sense; they can appear to have difficulties with or without a placard. But let's say it's obvious there are no visible issues and their response suggests they know what they're doing.
Option 1: call the police; if they get there very fast, it's a big fine. Great option if it worked, but the police usually aren't that fast, and people know that, and get away.
Option 2: park your vehicle behind theirs, blocking them in, until police arrive.
I asked a police dispatcher about this. They said if you're actively sitting in your car blocking them while they try to get out, that's 'taking them hostage', a more serious crime.
But if you park behind them and leave like going in the store, it's simply 'two illegally parked vehicles'.
Then she added she things the officers would not ticket you for it. That left only one main issue - escalation, i.e., the person rams your car, has a gun, etc.
Let's hear some thoughts on how to respond. One option is 'do nothing', another is 'leave it at telling them they're breaking the law' and try to get the police there fast in the rare case they can, third is to call the police and block them in, go in the store and keep an eye, and explain it to the police.