If you're talking to someone in a public park, and a stranger with a badge comes up and starts video recording your discussion while commenting "don't mind me,

If you're talking to someone in a public park, and a stranger with a badge comes up and starts video recording your discussion while commenting "don't mind me, it's just an administrative search", and this happens to pretty much everyone all the time, you DON'T respond with "well, there is virtually no situation in which you should have a reasonable expectation of privacy."