Others have told us in the past it would be a US Marshall with a court order, which makes it even more removed as C.Staley points out.
We have Federal Prosecutors, Sherriffs and Deputies, and Police who are hosts at their own shows. They all tell us that without a court order, no one has the right to ask to see your discs.
The old SPIN and KAPA organizations are now basically dead. These, at the demand of Sound Choice who controlled them and paid their bills, were acting with INTIMIDATION AUTHORITY, which is not a legal authority. They would try to catch you with a copied disc, then get you to sign "out of court" to never do that again. IF... someone signed, that converted from copyright law, which is very weak, to CONTRACT LAW which is AIRTIGHT! Don't ever sign such a document without legal counsel on your side reviewing the document. If any "authority actor" ever demands you sign something like that on the spot, have the Bar's Bouncer "escort" them outside and give them the option to leave or else...
But, if you have a bunch of illegal MIRC or other downloaded MP3+G songs, when someone does catch you, you'll be without ANY equipment. They can even take your van you transport it in and all your computers at your business or house! 
Playing MP3+G or ZIP files that you do not own the discs for, and do not have a legal invoice to prove you purchased them, IS... ILLEGAL and you will loose.