LONDON » Prince William and Kate Middleton’s aggressive legal strategy over topless photos of Britain’s likely future queen is the first salvo in what could be a decades-long tug-of-war over their family’s privacy.

A French court ruled in favor of the royal couple earlier today in their fight over the photos, but the scope of that ruling will be limited.

The unauthorized topless photos of Kate have already been widely published in France, Italy, Ireland and on the Internet — lessening the impact of Tuesday’s court injunction against future publication inside France.

The royals’ strong stance also included a bid to convince French prosecutors to launch a criminal inquiry to target the offending photographer.

The wealthy royal couple did not gain much on paper — the court-imposed fine was about $2,500 — but legal experts and royal watchers say the ruling was designed to demonstrate their willingness to use all legal means to prevent future press intrusion.

That will become even more important when the couple have a child, who would become third in the line of succession to the British throne, said Joe Little, the managing editor of Majesty magazine.

“This was done because they want to set a benchmark for the future,” he said.

“They want to send a warning to anybody who might think of doing something similar in the future.”

The fast legal intervention, which developed within hours of the publication of the photos Friday in a French gossip magazine, represents a break from Queen Elizabeth II’s traditional policy of using legal action only as a means of last resort. It also reflects William’s determination not to let the press harass Kate as it did his late mother, Princess Diana, Little said.

Still, the case shows the unlikelihood of controlling photos through legal means once they have been published.

Closer magazine was ordered to turn over all of its digital copies of the photos, but that has little meaning in a world where millions of copies can be made and distributed in the blink of an eye.

The revealing pictures will follow Middleton for the rest of her life — not unlike the snapshots of her appearance in a charity fashion show wearing black lingerie and a sheer dress during her university days.

“Clearly, the harm has been done,” said Christopher Mesnooh, an American lawyer working in France for Field Fisher Waterhouse. “Thousands, now tens of thousands of copies, are now in public circulation. A legal decision is a wonderful thing to obtain and the royal couple did exactly what they should have done. But you know the magazine is out there and I suspect most of you have already seen copies of that magazine, so the basic, the initial harm, has been done.”

He said magazine executives had concluded in advance they had little to fear from an adverse court ruling when they decided to print the photographs, obtained by a photographer who trained a long lens on the royal couple as they sunbathed on a private estate in southern France.

“Closer magazine has done a very sophisticated cost-benefit analysis,” Mesnooh said. “Whatever the amount of damages that a French court will award, it will be a fraction of the publicity that the magazine will have gained, as well as the number of issues of this particular issue of Closer magazine which will be sold.”

Tuesday’s ruling only affects the French magazine branch of Mondadori, Closer’s publisher. A French court ordered it to hand over all digital copies of topless photos of the Duchess of Cambridge within 24 hours and blocked further publication of what it called a “brutal display” of William and Kate’s private moments.

The court also stopped the magazine from republishing the pictures — including on its website and its tablet app — as well as re-selling them.

Mondadori faces a daily fine of $13,100 if it fails to do so.

“These snapshots which showed the intimacy of a couple, partially naked on the terrace of a private home, surrounded by a park several hundred meters from a public road, and being able to legitimately assume that they are protected from passers-by, are by nature particularly intrusive,” the French ruling decreed. “(They) were thus subjected to this brutal display the moment the cover appeared.”

The photos showed Kate relaxing at a private villa in Provence, in southern France, sometimes without her bikini top and, in one case, her bikini bottom partially pulled down to apply sunscreen.

The royal couple are also filing a criminal complaint against ‘X’ — the unnamed photographer who took the picture.

The suit aims to flush out the mystery photographer’s identity and prevent him or her from spreading the photos to new locations. If the case goes forward, the photographer could face a substantial fine and a one-year prison term.

But fines and prison terms won’t remove the photos from the Internet.

Professor Tim Luckhurst, head of the journalism department at the University of Kent, said the royal couple has likely learned some lessons from the debacle.

“The prince and his wife are going to have to think hard about what sort of conduct is acceptable for the heir to the throne and his wife in the age of the Internet,” he said.