UK broadband providers must now block access to Swedish BitTorrent file-sharing website The Pirate Bay.
Ruling in the High Court, Mr Justice Arnold decreed that the site - one of the largest databases in the world for pirated free music - infringes copyright.
The British Phonographic Industry (BPI) had sought a ruling that broadband providers should voluntarily block access to The Pirate Bay.
And BPI Chief Executive Geoff Taylor expressed satisfaction with the outcome of the case.
“The High Court has confirmed that The Pirate Bay infringes copyright on a massive scale,” he told the BBC.
“Its operators line their pockets by commercially exploiting music and other creative works without paying a penny to the people who created them."
Mr Taylor said this is "wrong", as musicians, sound engineers and video editors deserve to be paid for their work just like everyone else.
However Jim Killock, Executive Director of the Open Rights Group, described the decision to block The Pirate Bay as "pointless and dangerous".
"It will fuel calls for further, wider and even more drastic calls for internet censorship of many kinds, from pornography to extremism," he stated.
"Internet censorship is growing in scope and becoming easier. Yet it never has the effect desired. It simply turns criminals into heroes.”