My brush with law enforcement in a foreign country had to do with not obtaining a receipt for a piece of cheese.
In Italy, it is a law that one must receive a receipt for all transactions. One day in VCE, we saw a cheese vendor on the Strada Novo, not far from our hotel. We purchased a nice piece of cheese and suddenly were confronted by uniformed police from the Garda Finanza. It seems they were watching our transaction. They asked us to produce our cheese receipt (other uniforms were busting the cheese purveyors). When we could not produce our cheese receipt we were asked to produce our passports. At this point, it started to rain heavily and there was no way we would produce our passports for failing to obtain a receipt for a $2.00 piece of cheese. After much protesting in their fractured English and our fractured Italian, I think we just all wanted to get out of the rain and let the matter drop. Finally, they relented. They let us go, but shut down the cheese stand for the day.