By Jonathan Stempel

(Reuters) - Facebook users who employ the website's "like" feature to show support for a political candidate engage in legally protected speech, a U.S. appeals court said, reviving a lawsuit examining the limits of what people may constitutionally do online.

The 4th U.S. Circuit Court of Appeals ruled in favor of a former deputy sheriff in Hampton, Virginia, who claimed he lost his job in retaliation for his "liking" the Facebook page of a candidate running against his boss for city sheriff.

"Liking a political candidate's campaign page communicates the user's approval of the candidate and supports the campaign by associating the user with it," Chief Judge William Traxler wrote for a three-judge panel of the Richmond, Virginia-based appeals court. "It is the Internet equivalent of displaying a political sign in one's front yard, which the Supreme Court has held is substantive speech."

The case had been brought by six former employees of Hampton Sheriff B.J. Roberts, who claimed they were fired in violation of their First Amendment rights in retaliation for their having supported his opponent Jim Adams in a 2009 election.

Wednesday's decision revived claims by three of the six employees. It partially reversed an April 2012 ruling by U.S. District Judge Raymond Jackson in Newport News, Virginia, who called the "liking" of a Facebook page "insufficient speech to merit constitutional protection."

Among the allegations was that Roberts fired deputy Daniel Carter in retaliation for Carter's clicking the "like" button on a campaign page for Adams. A photo of Adams also appeared on Carter's Facebook profile in a list of pages that he "liked."

According to court papers, Roberts allegedly told Carter after learning about one of the Facebook entries: "You've made your bed, now you're going to lie in it, after the election you're out of here."

DOWN ON THE CORNER

In supporting Carter's bid for reinstatement, Facebook said the "like" button is crucial to the Menlo Park California-based social media company's more than 500 million users.

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It added that using the button to express support for a candidate is no different from standing on a street corner and announcing one's liking a candidate, which is protected speech.

Traxler agreed. "On the most basic level, clicking on the 'like' button literally causes to be published the statement that the User 'likes' something, which is itself a substantive statement," he wrote.

Facebook welcomed the decision.

"We are pleased the court recognized that a Facebook 'like' is protected by the First Amendment," Associate General Counsel Pankaj Venugopal said in a statement.

The American Civil Liberties Union also supported the former employees, as did the National Association of Police Organizations, which said Jackson's holding "unduly restricts the free expression and association rights of police officers."

James Shoemaker, a lawyer for the employees, did not immediately respond to requests for comment.

Jeff Rosen, a lawyer for Roberts, did not immediately respond to requests for comment.

The court ruled unanimously on the Facebook issue.

It said three of the six fired employees may pursue claims for reinstatement, but that Roberts was entitled to qualified immunity on their claims for money damages.

The appeals court upheld the dismissal of claims by the other three fired employees, finding no genuine factual dispute concerning their First Amendment rights. One judge dissented on the qualified immunity issue.

The case is Bland et al v. Roberts, 4th U.S. Circuit Court of Appeals, No. 12-1671.

(Reporting by Jonathan Stempel in New York; editing by Andrew Hay)