OK! magazine has partially won an appeal at the House of Lords in its battle with rival Hello! over Catherine Zeta Jones's wedding photos.
The Hollywood couple are no longer involved in the case
Law Lords ruled Hello! breached OK!'s confidentiality when it published shots of her wedding to Michael Douglas. OK! bought the rights to the event in 2000.
The decision could affect future media coverage of public figures who have signed exclusive deals.
But the Lords disagreed with OK!'s claim that its business had been hurt.
OK! paid £1m for the exclusive rights to pictures from the wedding of the couple, who were not involved in the latest hearing.
But Hello! spoilt the scoop by publishing photos taken by somebody pretending to be a guest or a waiter.
OK! claimed in the Lords that Hello!'s use of surreptitious photography was unlawful interference with its business or a breach of its right to confidentiality. Three out of five Law Lords found in OK!'s favour.
18 November 2000 The wedding takes place in New York - an exclusive deal with OK! magazine is agreed
7 November 2003 OK! wins over £1m in damages from Hello! at the High Court
18 May 2005 The Court of Appeal overturns the decision, OK! is ordered to pay back damages and costs
2 May 2007 The House of Lords makes a partial ruling in favour of OK! magazine
Lord Hoffman said OK! was entitled to expect that guests and staff at the wedding would not breach its exclusive rights to publish photographs of the event.
"I cannot see why they were not entitled to enforce it," he said.
He said other Law Lords were troubled by the fact that the images were not intended to be kept secret, but were to be published by OK!
"But I see no reason why there should not be an obligation of confidence for the purpose of enabling someone to be the only source of publication if that is something worth paying for," he explained.
"Why should a newspaper not be entitled to impose confidentiality on its journalists, sub-editors and so forth to whom it communicates information about some scoop which it intends to publish next day?"
Lord Hoffman said the photographs comprised information of a commercial value over which the couple could impose an obligation of confidence, adding that it did not create an "an image right" to protect the Douglases or their private life.
"Some may view with distaste a world in which information about the events of a wedding... should be sold in the market in the same way as information about how to make a better mousetrap," he said.
"But being a celebrity or publishing a celebrity magazine are lawful trades and I see no reason why they should be outlawed from such protection as the law of confidence may offer."
Caroline Kean of Wiggin media lawyers said the ruling might spell the end of rival magazines trying to outdo each another for exclusive pictures.
"I think it's likely that nobody is going to go into a 'spoiler' without very careful consideration," she said.
"If somebody else is getting shots in the full knowledge that you've got an exclusive buy-up on the event, they are going to have to pay you damages because of that."
The tight security which has become commonplace at celebrity weddings could be relaxed, she added.
"Within reason if you've got it in a private place, you can stop expecting people coming in and taking undercover shots and selling them to rivals, which is what has happened in the past," she said.
OK! signed a deal to obtain exclusive coverage of the wedding celebrations in New York on 18 November 2000.
It took legal action after Hello! published the "spoiler" pictures. It won over £1m in damages three years later, after a judge decided the unofficial publication had caused commercial damage.
But Hello! successfully challenged the order in the Appeal Court in May 2005, arguing that "spoilers" were a well-known tactic in the newspaper and magazine industry. OK! was ordered to pay back damages, costs and interest amounting to almost £2m.
After the original 2003 hearing, the Hollywood couple were awarded £14,600 after Ms Zeta Jones told the court she felt "devastated" and "violated" when she discovered "unflattering" paparazzi pictures had been taken.