Correction: A previous version of this story incorrectly referred to a photograph of Prince Harry taken during a poker game; he was playing billiards. This version has been corrected.

A photographer armed with a telephoto lens takes a series of photos of a semi-nude celebrity lolling about a private estate and sells the photos to a sensation-loving publication.

Question: Does the behavior of the shooter violate the law? Does the publication’s?

The British royal family commenced an extraordinary legal offensive Monday, arguing that topless photos of Kate Middleton were taken illegally and that further publication of the pictures is an invasion of privacy that should be stopped by a court.

The court, in this case, is located in France, and French law appears to favor the royals’ case against the owners of Closer, the French magazine that first published the Middleton photos last week.

On Monday, the Italian magazine Chi added to the palace’s heartburn by publishing a 26-page spread of grainy, telephoto-lens images of the Duchess of Cambridge sunbathing topless in France. It thus became the third European publication to print a portion of the series, which is said to number some 200 snaps.

At the same time, attorneys for Middleton and her husband, Prince William, filed a criminal complaint and a civil action against Closer and the still-unidentified photographer who took the pictures. The royals are seeking to stop publication of more photos by the French magazine, which is owned by a company controlled by former Italian prime minister Silvio Berlusconi. The same company owns Chi, which published its spread with the headline “The Queen is Nude.”

The royals contend that the photos of Middleton — apparently taken by a single paparazzo — violate her privacy and that the photographer trespassed on the private French estate where she and Prince William were vacationing. The editor of the Italian magazine disputes the trespassing allegation, saying the photos were shot from a public road.

American civil law is fairly clear on this sort of thing: You can be held liable for photographing someone in a private setting without his or her knowledge or consent. The American Law Institute, in summarizing court decisions, says the photographer’s actions could amount to an “intrusion upon seclusion,” a civil offense.

But publishing such photos may be another matter, says Eric Easton, a law professor at the University of Baltimore’s School of Law. “Courts are very reluctant to silence newsworthy speech, even if [the speech] has the effect of disturbing someone,” he said.

Although the Middleton photos are easily available around the world to anyone with an Internet connection, no British media have been willing to defy the royal family and publish them.

Only one British paper, the popular tabloid the Sun, owned by Rupert Murdoch’s News International, published photos of Prince Harry naked in his Las Vegas hotel room during a strip billiard party last month. But the Sun has ruled out reprinting the Middleton photos.

The photos of Harry probably don’t raise the same privacy and public-relations concerns in Britain as those involving Middleton, British media sources suggested Monday.

The British press traditionally has respected the privacy of members of the royal family when they are out of the public eye, as William and Kate were when they were shot on a well-guarded estate in Provence. By contrast, Prince Harry invited strangers with cellphone cameras to his hotel room, forgoing some expectation of privacy.

The matter also comes up amid the lengthy phone-hacking scandal in Great Britain, which has revealed extensive government corruption and ignited widespread public outrage about the sometimes-illegal news-gathering methods of the Murdoch-owned press.

As a result, “I don’t think any Brit outlet will touch” the Middleton photos, said Alan Rusbridger, the editor of the independent Guardian newspaper.

French privacy laws are considered among the strictest in Western Europe; the French Criminal Code specifies punishment of a year in prison and a fine of up to 45,000 euros ($59,000) for the “willful violation of the intimacy of the private life of other persons” as a result of “recording or transmitting the picture of a person who is within a private place, without the consent of the person concerned.”

Civil damages for privacy violations in France have typically been low, far less than the top criminal fine, said Gillian Phillips, director of editorial legal services for the Guardian’s parent company.

Phillips said she believed it was “highly likely” that the royal family could succeed with its claims against Berlusconi’s magazine company, Mondadori Media.

But Marina Berlusconi, the former prime minister’s daughter’s daughter and Mondadori’s chairwoman, said in a letter to the Italian newspaper La Repubblica that her company “did its job” in upholding freedom of the press by publishing the photos.

Chi’s editor, Alfonso Signorini, told the Telegraph, a British newspaper, that the photos were a “nonviolation of privacy because they were taken from a public space . . . the photos are absolutely within the confines of the Italian law.”

Some of the photos obtained by Closer were republished last week by the Irish Daily Star. In response, the tabloid newspaper’s co-owner, British media baron Richard Desmond, has threatened to pull out of the joint venture that owns the paper, which could lead to its shutting down.