Dont tresspass or no trespassing

[Grimnir]

A while ago I stumbled over a long running story called something like "Dont tresspass" or "No trespassing" about federal officers who run into a lot of problems because they ask the wrong questions at the wrong place - and say no thank you to the offer of a free drink at a local bar. I do not remember who wrote it, where I saw it and it does not seem like the author is here. Does anybody recognize the description or know if the author is still active somewhere?