I've been to many lan parties in my day. Some of the largest in the world, in fact. And I will be attending MML 5, where the World Series of Video Games will be held.
With commercial established LAN's, the written policy has always been against piracy as a whole. It's just the establishment's waiver from any legal responsibility. It wouldn't hold up in court, though.
Piracy has been a part of LAN parties for as long as they have existed. In fact, many people I know attend them purely for the "free" software.
As far as I know, if this were to happen in the US, each individual would have the opprotunity to deny all charges and claim breach of the 4th Ammendment. Things like this can get sticky, especially when judges are completely uneducated about technology.
Anyway, if anyone lives in the midwest/east coast, you might want to check out Million Man Lan 5. It's being held in Louisville, Ky (as always). There should be about 4000 people there, give or take. More info here:
http://www.lanwar.com/FAQ.asp?Process=DISPLAY&FAQID=12
If anyone is interested, hit me with a PM and we can meet up or something.
Hey, maybe Hak.5 could shoot a few segments at the event and interview some geeks. :)