In the age of Twitter, can no sin remain secret?

Few know the answer better than Ryan Giggs. The married soccer star sought and won an injunction that barred London’s feisty tabloids from publishing his name in connection with a dalliance. But then the users of Twitter rose up like a Greek chorus, dispatching electronic missives that unmasked Giggs as the Don Juan of the pitch.

Even as British newspapers remained legally gagged, the affair became Britain’s worst-kept secret, inspiring jeers from fans at matches and, ultimately, Giggs’s public naming and shaming in Parliament late last month.

The episode marked the latest challenge by Twitter users to Britain’s privacy laws, a drama that is testing the viability of rules drawn up in an era of old media.

With a barrage of tweets, ­social-media users are blasting holes in a system that has long shielded Britain’s rich and famous from scandal, leaving the powerful and naughty here quaking in their Gucci loafers. In one assault, a Twitter vigilante last week named names and released the lurid misadventures of a whole new batch of British celebrities and politicians allegedly holding media gag orders.

The challenge has left British judges and wronged parties scrambling for ways to hold new media accountable. Last week, one British town used the California legal system to force San Francisco-based Twitter to release the names of four users who allegedly libeled its council members. And while Giggs’s paramour has confirmed the affair, the soccer star is using the London court system to go after anonymous Twitter users in what may end up being a test case.

“Are you really going to say that someone who has a true claim for protection perfectly well made has to be at the mercy of modern technology?” Igor Judge, head of the English judiciary, told reporters in London. “I’m not giving up on the possibility that people who peddle lies about others through using technology may one day be brought under control, maybe through damages, very substantial damages.”

The debate here is casting a light on what critics call Britain’s excessive privacy laws.

Meant as a tool to defend reputations in the face of an aggressive tabloid press, an injunction effectively prevents libel or infringement of privacy before it happens for those who can afford the legal firepower needed to win one.

They are a public figure’s dream, stopping scandal in its tracks. For instance, if the United States offered similar legal recourse, Rep. Anthony Weiner (D-N.Y.) might have had a case to win an injunction and gag the media from reporting the leak of a compromising photo — that is, if his Twitter account had actually been hacked as he initially claimed. The key is the dissemination of embarrassing information against one’s will. Thus, the fact that he sent out the photo himself probably would have precluded him from winning an injunction, according to British legal experts.

But even in Britain, with new media such as Twitter, that kind of privacy protection is slipping from the grasp of the rich, famous and powerful.

Media gag orders here are not new. But they burst into the public eye in October 2009 after the oil trader Trafigura obtained a “super-injunction” to block the Guardian newspaper from publishing stories connecting the company to the dumping of toxic waste. It did not, however, stop scores of Twitter users from sending out messages pointing the finger at the company by name.

Since then, a slew of injunctions has involved the personal lives of celebrities, corporate titans and politicians, with incidents ranging from suicide attempts to extramarital affairs.

News organizations and civil rights groups have condemned them as closed-door justice and infringements on free speech. A panel of Britain’s senior judges last month issued a warning about the proliferation of such gag orders, suggesting their number be contained. Some orders allow the news media to report on incidents but without naming names. Super-injunctions, meanwhile, impose near-total media blackouts. The list of those who have used injunctions to shield their personal lives include celebrity journalist Andrew Marr and former Royal Bank of Scotland chief Sir Fred Goodwin. But no case has garnered more attention than that of Giggs, who plays for Manchester United.

The soccer star won an injunction on April 14 forbidding the tabloids from naming him in connection with an affair with Imogen Thomas, a Welsh model and reality-show celebrity. Within six hours of that injunction being issued, some Twitter users began to tweet about the affair and name Giggs.

In early May, one user going by @injunctionsuper tweeted not only about Giggs but also about other personalities with gag orders. That prompted an avalanche of Twitter users — including high-profile “Twitterati” such as CNN host Piers Morgan — to unmask Giggs.

Legislator John Hemming, invoking parliamentary privilege, referred to Giggs on the floor of the House of Commons last week, arguing that the rise of Twitter had made such media injunctions obsolete. “With about 75,000 people having named Ryan Giggs on Twitter, it is obviously impractical to imprison them all,” Hemming said.

Echoing Hemming, Prime Minister David Cameron has called the injunctions “unsustainable,” saying Parliament should reexamine them. He added, however, “that I'm not sure there is going to be a simple answer.”

Giggs’s lawyers declined to comment, as did Twitter officials in San Francisco. But court officials said the athlete has filed a lawsuit in London seeking to force Twitter to hand over details of the anonymous users who named him. Underscoring the difficulty of regulating a social media network made up of millions of independent users worldwide, legal experts are calling his chances of success a long shot.

Under legal duress, Twitter has been known to disclose the names of users — a possibility outlined in its terms and conditions — in specific cases involving alleged crimes that could violate U.S. law. But Britain’s media gag orders, scholars say, has no clear parallel in U.S. law, making it difficult to see how a London court could compel the company to release the names of users who defied it.

“What’s going on with Twitter is a very public response to a lot of concern about super-injunctions,” said Gillian Black, professor of media and commercial law at the University of Edinburgh. “But the problem is, no one knows how Twitter can be controlled, if that’s what we want to do.”