Hello! magazine has won its challenge to a court order that it must pay OK! £1m in damages for using pictures of Catherine Zeta Jones' wedding.
Catherine Zeta Jones and Michael Douglas wed in New York in 2000
The publication admitted it had used snatched photos of the wedding to spoil rival OK's exclusive coverage.
Hello! argued that "spoilers" were a well-known tactic in the newspaper and magazine industry.
A judge awarded the £1m damages last year after ruling that Hello! had caused commercial damage to OK!
It came after a six-week High Court hearing in 2003 at which Zeta Jones said she and husband Michael Douglas had signed an exclusive £1m wedding coverage deal with OK! after turning down a higher offer from rival Hello!
She said she felt "devastated, shocked and appalled" when unauthorised photographers then gatecrashed their New York wedding in November 2000.
A judge ruled that Hello! had breached the film stars' rights of privacy and ordered the magazine to pay Zeta Jones and Douglas £14,600.
Hello! was also ordered to pay more than £1m damages plus another £1m in legal costs to OK! magazine.
But last December James Price QC, representing Hello!, told the Court of Appeal that "spoilers" were not previously considered unlawful.
"What happened to Hello! was that it was caught by a law which said 'stop it' retrospectively," he told the court.
Mr Price also argued that "spoilers" could give the magazine in question a commercial advantage.
"One can get a promotional boost from very obviously inferior pictures of an event in a competing publication," he said.
On Wednesday Lord Philips upheld the Hello! appeal, ruling that its publication of the photographs had not breached OK!'s commercial rights.
Hello!'s appeal against the damages awarded to Zeta Jones and Douglas was dismissed, however.
The appeals court also threw out the Hollywood couple's claim for more damages and OK!'s appeal against a ruling that it was entitled to only 75% of its legal costs against Hello!
After the ruling, Hello! lawyer Chris Hutchings said: "It's a good thing that the law which had been introduced so far as making spoilers outlawed has now been revoked.
"We certainly believe that competition is a good thing in the media."
However, OK! magazine lawyer Maninder Gill said the ruling would have an impact on all publishers with exclusive rights as it means rivals can run spoilers with no redress in law.
He said: "It's an area of law that has to be clarified as soon as possible.
"There's a long way yet in this case and there's a question of law that the House of Lords has to decide. So there's a lot to fight for."