The Supreme Court on Thursday weakened the longstanding “knock and announce” rule under which police must in most circumstances knock on the door, announce their presence, and wait briefly before forcibly entering a house with a search warrant.

Although not repealing the rule itself, Justice Antonin Scalia’s 5-4 majority opinion said the traditional remedy for police violation of the rule — namely, barring the use at trial of the evidence found — is no longer required.