With remarkable speed and unanimity, the Supreme Court on Tuesday ruled that in ordinary circumstances, an anonymous tip to police that a person is carrying a firearm is not enough to trigger a lawful “stop and frisk” search.

Ruling in Florida v. J. L., which was argued less than a month ago, Justice Ruth Bader Ginsburg wrote that the Court would not create an “automatic firearm exception” to the normal need to establish the reliability of an anonymous tip before acting on it.