WASHINGTON—In a unanimous 9-0 ruling Friday, the Supreme Court upheld a controversial federal law allowing licensed judges to carry concealed gavels in public. “It is the opinion of the court that any judge, magistrate, or justice found to be of legal age and sound mind who so desires to carry in secret an adjudicating mallet on his or her person, provided such gavel is properly permitted and registered within the local jurisdiction, shall face no legal encumbrances—federal, state, or otherwise—preventing them from so doing,” Chief Justice John Roberts, an outspoken pro-gavel advocate, wrote for the majority. “Whether such an arbitrating implement be used to conclude trial proceedings, commence an adjournment, for self-defense, or purely for sport, the right of any and all judicial officials to harbor a concealed gavel, and the lawful use thereof, is wholly and fundamentally protected under the Constitution of the United States.” Under the terms of the ruling, all varieties of gavel—even automatic or sawed-off models like the ones used in several recent high-profile mass bonkings—will remain legal for judges to carry.