Hello! has challenged why it had been ordered to pay more than A£1 million in damages to a rival celebrity magazine for publishing paparazzi pictures of the wedding of Catherine Zeta Jones and Michael Douglas.
Hello! admitted the snatched pictures were published as a "spoiler" to lessen the impact of OK! magazine's exclusive A£1 million contract with the Douglases to cover the New York ceremony.
James Price QC, representing Hello!, told three judges at the Court of Appeal that "spoilers" were a well-known tactic in the newspaper and magazine industry and his clients had been victims in the past.
"This was something previously not considered unlawful. We are in the position that if you are going to compete in this industry you have to publish spoilers.
"But what happened to Hello! was that it was caught by a law which said 'stop it' retrospectively."
The ruling against Hello! came after a six-week High Court hearing last year at which the 35-year-old actress told how she felt "devastated, shocked and appalled" when she realised unauthorised photographers had gatecrashed her wedding at the Plaza Hotel in November 2000.
She said she and her 59-year-old husband had signed the deal with OK! after turning down a higher offer from Hello!
Mr Justice Lindsay ruled that Hello! had breached the couple's rights of confidence but they had no claim in law for invasion of privacy.
He awarded the couple a total of just A£14,600 but OK! got A£1,033,156 for what the judge said was commercial damage to its expected exclusive coverage.