The case is Bland v. Roberts, 12-1671, U.S. Court of Appeals for the Fourth Circuit (Richmond), reported by Bloomberg:

Using Facebook Inc. (FB)’s “Like” feature to show support for a candidate in an election is protected speech under the U.S. Constitution, a federal appeals court said.

The U.S. Court of Appeals in Richmond, Virginia, issued its ruling today in a lawsuit brought by former employees of a sheriff’s office who said they lost their jobs because they supported their boss’s opponent, including by endorsing a campaign page on Facebook.

The appeals court reversed a lower court judge who said that simply clicking the “Like” button on a Facebook page didn’t amount to “a substantive statement” that warrants constitutional protection.

“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,” U.S. Circuit Judge William Traxler said in today’s ruling. “It is the Internet equivalent of displaying a political sign in one’s front yard, which the Supreme Court has held is substantive speech.”

In simple terms: using Facebook’s “Like” is protected under the 1st Amendment.