The selling of "mod chips" for Sony PlayStation 2 game consoles has been ruled illegal by a UK high court.
The chips allow imported copies of PS2 games to be played
A PlayStation 2 with a modified chip installed can play imported or pirated copies of the console's video games.
Mr Justice Laddie backed Sony's legal argument that its intellectual property was being infringed by people selling the chips to console owners.
The ruling is thought to be one of the first brought under a controversial European Union directive on copyright.
Sony brought its case against a man called David Ball who was accused of selling about 1,500 "Messiah" mod chips.
In the High Court, Mr Justice Laddie ruled that Mr Ball was acting illegally in selling the chips which get around the built-in copy protection system on Sony's console.
As well as declaring the sale of the mod chips illegal, Mr Laddie said that the use, advertising or possession of them for commercial purposes should be considered illegal too.
Sony brought the case under the EU Copyright Directive which was enacted in the UK in October 2003.
Under that directive, it is illegal to circumvent copy protection systems. But some cyber-liberties advocates claim that such laws only enshrine existing monopolies.
They say that neither professional criminals nor technically savvy users will be deterred by such legislation.
The ruling is not the first victory Sony has won against makers of mod chips. In Belgium it also won a similar case against another mod chip seller.
However, in Italy a judge threw out Sony's case saying it was up to owners of a console what they did with it.
Similarly in Spain, mod chips are seen as legal despite the EU copyright legislation.