The ONLY thing to do when police ask you to remain/detain is to say: a) Am I free to leave? (If so, leave at once.) b) Am I under arrest? On what charges? c) I am exercising my right to remain silent pending legal counsel. (It sounds ridiculous to SAY "I am exercising my right to remain silent", but apparently you have to explicitly say that, as otherwise a judge may decide you didn't exercise this right and were just obstructive.)
Unfortunate second-hand experience.
Not trying to trump anyone with first-hand experience. But after reading the linked article I wonder what would've happened if every patron in the bar had refused to give up their ID and wait for it to be returned? Because this was definitely a breach of the 4th amendment. That said, I know the 4th amendment means squat in a given bar, on a given night.
