Hello! magazine has challenged a court ruling which forced them to pay more than £1 million in damages to Catherine Zeta Jones and Michael Douglas.
Catherine Zeta Jones and Michael Douglas wed in New York in 2000
Lawyers for the publication admitted that they had used snatched photos of the couple's wedding to spoil rival OK's exclusive coverage of the event.
But James Price QC told the Court of Appeal on Monday this was not unlawful.
A judge ruled last year that Hello! had
breached the film stars' rights of confidence and awarded the damages.
Zeta Jones and Douglas were awarded £14,600, while OK! magazine was awarded more than £1 million due to commercial damage inflicted on its coverage.
Mr Price, representing Hello! magazine, told the Law Lords hearing the case that the practice of "spoilers" was common in the publishing world.
"We are in the position that if you are going to compete in this industry you have to publish spoilers," he told the court.
"But what happened to Hello! was that it was caught by a law which said 'stop it' retrospectively," he added.
Zeta Jones and Douglas claimed for "personal distress"
Mr Price also argued that spoilers could give the magazine in question an advantage.
"One can get a promotional boost from very obviously inferior pictures of an event in a competing publication," he said.
Mr Price added that the High Court judge who made the ruling against Hello! said that OK! had lost 1.4 million sales from the spoiler.
But Mr Justice Lindsay had also accepted that a spoiler could have the effect of increasing the sales of a magazine with an exclusive contract.
Mr Price said this made his original findings "manifestly unsustainable".
If the Appeal Court challenge is successful, then both OK! and the Douglases stand to lose their damages.
OK!, meanwhile, is challenging a ruling that entitled it to only 75% of its legal costs for its case against Hello!
The cost of the case so far has been estimated at £4 million.
Actress Zeta Jones, 35, had said in the original hearing that she and her 60-year-old husband accepted the OK! deal after turning down a higher offer from Hello! magazine.
The actress had added how she felt "devastated, shocked and appalled" when she realised her wedding ceremony had been gatecrashed by uninvited photographers, prompting the legal action.
The current hearing, scheduled to last up to five days, was adjourned until Tuesday.