If you are smoking marijuana at home when you hear a loud knock and the word “police,” don’t make a sound unless you want to buy a new door and have your place searched without a warrant. That is the message from the U.S. Supreme Court this week in King v. Kentucky, 563 U.S. ___ (2011).

In this latest “exigent circumstances” exception to the need for a search warrant under the Fourth Amendment, Louisville police were conducting a controlled drug “buy” when their suspect ran into one of two apartments. Selecting the unit from which they smelled burnt cannabis emanating, police knocked loudly and declared their presence. Hearing movement inside that they concluded was persons destroying narcotics, they broke in without a warrant. In an 8-to-1 ruling, Justice Alito wrote that this was permissible conduct. Justice Ginsburg filed a dissent.

If I understand correctly, it makes no difference how police single out your residence provided there is no actual or threatened Fourth Amendment violation associated with their selection, like thermally imaging your grow-lights. Police can arrive because your window was ajar, you did not pick up your newspaper, or they just happen to be in the neighborhood. Once cops smell anything illegal (or a dog does), all they need to lawfully force entry consists of one-two-three: Knocking, announcing, and hearing any noise that reasonably suggests you are destroying evidence.

Okay, let’s imagine you are smoking a joint and the police knock. What can you do to save your front door from destruction 15 or 20 seconds after law enforcement bangs on it? You would need to “stand on [your] constitutional rights,” in the words of Justice Alito. It appears that if your living unit remains absolutely silent, law enforcement must obtain a search warrant. Alternatively, if you ask the officers face-to-face or through the closed door if they have a warrant, and they don’t, you can tell them to go away. The one thing you better not do is flush the toilet!