“Liking” something on Facebook is a form of speech protected by the First Amendment, a federal appeals court ruled Wednesday, reviving a closely watched case over the extent to which the Constitution shields what we do online. In doing so, the Fourth U.S. Circuit Court of Appeals sided with a former deputy sheriff in Hampton, Va., who said he was sacked for “liking” the Facebook page of a man running against his boss for city sheriff. “Liking” the campaign page, the court said, was the “Internet equivalent of displaying a political sign in one’s front yard, which the Supreme Court has held is substantive speech.” The Richmond-based appeals court reversed a ruling by a federal district judge, Raymond A. Jackson, who threw out the lawsuit last year on the grounds that a Facebook “like” was “insufficient speech to merit constitutional protection.”