LONDON—The recent scandal in the United Kingdom surrounding alleged celebrity indiscretions and a type of media gag order is raising some tricky questions about defamation and liability, particularly regarding social media.

Confusion over the scope of U.K. privacy law arose after the recent identification on microblogging platform Twitter of a famous soccer player who had secured a so-called superinjunction to prevent details of his private life being made public. His subsequent naming during a session of Parliament added to the confusion over when and how his identity could be discussed publicly under the rules for superinjunctions.

A superinjunction is an interim injunction granted by U.K. courts to prevent the publication of information about an individual that is deemed to be confidential or private. In addition, the order bars publication of—or even informing others about—the existence of the order.

While media companies likely have insurance that would be triggered if they are accused of libel or defamation in connection with the incident, companies that are not traditional publishers also could be held liable for content they or their employees post on websites or social media sites, experts say.

Additionally, if companies are found guilty of contempt of court for violating a superinjunction issued by a U.K. court, they may find themselves uninsured for legal costs.

A superinjunction is intended to ensure that the outcome of U.K. legal proceedings is not prejudiced by publication of certain information, said Danvers Baillieu, a media lawyer at Pinsent Masons L.L.P. in London.

In the case of the soccer star, the fact that he had taken out a superinjunction and tried to suppress allegations about his private life were made public in May by a Twitter user, whose message was forwarded—or  “retweeted”—numerous times.

Also in recent weeks, details of several other superinjunctions protecting celebrities have been made public on social networking sites.

Late last month, Scottish newspaper the Sunday Herald printed a thinly disguised photograph of the soccer star and said that, while it did not accuse him of any misdeeds, it decided to reveal his identity because it believed it is “unsustainable that the law can be used to prevent newspapers from publishing information that readers can access on the Internet at the click of a mouse.” The Sunday Herald's ultimate parent is McLean, Va.-based media conglomerate Gannett Co. Inc.

Separately, London-based publisher News Group Newspapers Ltd., which is a unit of New York-based media giant News Corp., sought to have the soccer star's superinjunction lifted, but Justice Sir David Eady rejected the request on May 23.

Later the same day, a member of Parliament, John Hemming, named Ryan Giggs as the soccer star in the House of Commons. Mr. Hemming is protected by parliamentary privilege, which allows MPs to speak freely during proceedings of Parliament without fear of legal action alleging slander or contempt of court.

Media outlets then revealed the soccer star's name, using what is known as “qualified privilege.” That principle protects against libel or slander claims as long as the information revealed under parliamentary privilege is reported accurately, said Andrew Horrocks, a partner at London-based law firm Barlow Lyde & Gilbert L.L.P.

Meanwhile, English courts have granted the soccer star's request to ask San Francisco-based Twitter Inc. for information about users who sent tweets using his name.

The situation, said Christopher Wolf, a partner at Hogan Lovells L.L.P. in Washington, raises interesting questions about what legal jurisdictions apply in Internet publishing cases. So far, he said, there is no real guidance about the reach of a country's courts and which jurisdictions would apply in cases of this kind.

Companies must, therefore, ensure they have risk processes in place to ensure that their employees are not falling foul of international privacy and libel laws when using social networking sites on company computers.

Twitter, Mr. Baillieu pointed out, is not being sued, but merely is being asked to provide information. Other platforms previously have provided such information when asked to do so by the courts, he said.

The question of the extent to which Twitter and other social networking platforms are deemed to be publishers is “still being worked at from a legal point of view,” said BLG's Mr. Horrocks.

But the case involving the soccer star involves potential liabilities of which traditional media outlets and other companies should be aware, he said.

In naming the subjects of U.K. superinjunctions, companies risk libel and defamation actions as well as a contempt of court citation, he said.

Media companies can purchase liability insurance that will cover them for all content, including user-generated content, that they publish or broadcast, said Sarah Neild, a vp at Marsh Ltd. in London.

They likely are aware how the U.K. qualified privilege law can protect them and made sure that they did not break the law by publishing the soccer star's name, she said.

However, any media company that breaches a superinjunction is almost certain to have done so deliberately, she said. In such cases, coverage would not respond.

Legal gray areas exist, however, when it comes to Internet service providers or social networking platforms that are not traditional publishers but that might be deemed to be publishing information, said Lisa Hansford-Smith, a vp in Marsh's FINPRO division in London.

In a previous U.K. case where users of ISPs made public details about two notorious juvenile criminals whose identity was protected, ISPs were warned by the courts to remove certain content, said Leah Alpren-Waterman, a professional support lawyer at BLG.

While ISPs or telecommunications companies can argue that they are simply platforms and not publishers per se, much will hinge on what action is taken in the light of the recent superinjunction breaches by social networking site users, Ms. Hansford-Smith said.