The Motion Picture Association (MPA) has succeeded in forcing British ISP BT to block access to the Newzbin 2 pirate website.
Newzbin 2 has about 700,000 users and has been making over £1 million a year, says the MPA, by providing links to pirated movies, TV shows, music and software through its members-only site.
"In my judgment it follows that BT has actual knowledge of other persons using its service to infringe copyright: it knows that the users and operators of Newzbin 2 infringe copyright on a large scale, and in particular infringe the copyrights of the studios in large numbers of their films and television programmes," said Mr Justice Arnold in his ruling.
"It knows that the users of Newzbin2 include BT subscribers, and it knows those users use its service to receive infringing copies of copyright works made available to them by Newzbin 2."
The ruling orders BT to use its CleanFeed system - designed to block child porn - to block sites on the IP address level. And because BT also supplies the CleanFeed system to other ISPs, the way's now clear for the MPA to go after them too.
Indeed, the floodgates could open, which worries organizations such as the Open Rights Group.
"Website blocking is pointless and dangerous. These judgements won't work to stop infringement or boost creative industries," says Peter Bradwell, ORG copyright campaigner.
"And there are serious risks of legitimate content being blocked and service slowdown."