WASHINGTON — The Supreme Court on Thursday struck down a federal law that made it a crime to falsely claim being awarded a top military honor, saying the law infringed on the Constitution’s First Amendment protection of free speech.

The court ruling concerned the Stolen Valor Act, under which a California man, Xavier Alvarez, was convicted for claiming falsely in 2007 that he had been awarded the Medal of Honor, the nation’s highest award for valor. But Alvarez’s attorneys convinced a lower court that his untruths were protected by the First Amendment’s guarantee of free speech. On Thursday, the Supreme Court agreed.


‘‘The Act seeks to control and suppress all false statements on this one subject in almost limitless times and settings,’’ the court wrote. ‘‘Permitting the Government to decree this speech to be a criminal offense would endorse government authority to compile a list of subjects about which false statements are punishable.’’Jan Scruggs, founder of the Vietnam Veterans Memorial Fund, which built the Wall, commented in an e-mail: ‘‘The Court has ruled that the First Amendment protects a wide range of obnoxious behavior including this.” Other veterans groups expressed dismay.

The Supreme Court in recent years has been protective of speech rights in several high-profile cases.