I’d probably sit on my porch in a pair of Daisy Dukes and clean one of my AK’s.
Now that’d scare me off.
(The Daisy Dukes, not the AK.)
I’m not aware that P.I.'s have any real authority, despite what you see on television. At best they could execute the same citizens arrest that you and I could. But that doesn’t mean that they don’t have a right to be in public as long as there’s no evidence that they’re about to do something wrong. And, yeah, I don’t want some suspicious car out in front of my house, either, but frankly there’s no really anything I could do about it.
I’m not really sure what authority has to do with anything.
Also, not all surveillance is meant to be covert.
I won’t have to do a single thing. My bat-shit crazy cat lady neighbor will be along shortly to spew obcenities at the car and eventually defecate on the hood and smear the result on the windshield if she does not get the response she wants.
I’m only 1/2 kidding about this.
I don’t think PIs have any more licence than ordinary citizens to break the right to privacy.
I concur. Whose privacy is being violated in the OP’s scenario?
Do about it? Nothing.
He’s legally parked in a public place. He could be meditating, cooling down after a fight with his s/o, needing a break or time to think, trying to serve a summons, working up the nerve to tell his wife he lost his job, whatever. If he’s not causing trouble (and sitting quietly while legally parked insn’t my idea of trouble) then live and let live.