Players discovered hidden sex scenes in GTA

Citing freedom of speech worries US district judge Ronald Whyte granted an injunction to stop the law coming into force on 1 January.

Judge Whyte also questioned whether it was possible to ban sales to minors.

The ruling comes as US politicians draft national laws to stop the sale of adult-themed games to children.

Courtroom battle

The Californian law was drafted in October and aimed to make it a crime for games that "depict serious injury to human beings in a manner that is especially heinous, atrocious or cruel" to be sold or rented to those under 18.

Signed into law by California Governor Arnold Schwarzenegger, the measure imposed $1,000 (£575) fines every time it was broken.

The passing of the law was challenged by the Entertainment Software Association and the Video Software Dealers Association which represent game makers and retailers.

The two organisations filed a lawsuit claiming that the law risked breaking free speech statutes.

In granting the injunction, Judge Whyte said the two groups could be right in saying it risked breaking such laws.

ESA president Doug Lowenstein said: "For the sixth time in five years, federal courts have now blocked or struck down these state and local laws seeking to regulate the sale of games to minors based on their content, and none have upheld such statutes."

Other rulings on violent or sexually-themed games have been proposed in several US states including Illinois and Michigan.

The injunction only delays the introduction of the law and now both sides in the row will get a chance to argue their case before a court. Backers of the law said Judge Whyte's block was only a "temporary pause".

The rash of attempts to limit sales of such games came after explicit sex scenes were found in the PC version of GTA: San Andreas. The discovery of the scenes led to that game being re-rated as an adults-only title.

The push for national laws on the sale of adult-themed games to children is being spearheaded by Senator Hilary Clinton who believes that the computer game industry's self-rating system was not working.