The Supreme Court has ruled that police use of a drug-sniffing dog on a homeowner's porch is a violation of the Fourth Amendment's protection against unreasonable searches and seizures.

The case, Florida v. Jardines, involved police taking a drug-sniffing dog to Jardines’ front porch, where the dog gave a positive alert for narcotics.

The officers subsequently obtained a warrant for a search, which revealed marijuana plants, and Jardines was charged with trafficking in cannabis. The Supreme Court of Florida approved the trial court’s decision to suppress the evidence because of a search without probable cause.

The government argued that the dog is "alerted" only by illegal contraband so it didn't count as a search. But Justice Scalia's majority opinion noted that a homeowner's rights extend to their porch, so the search was an intrusion unsupported by probable cause.

A Supreme Court precedent has changed slighty: "Every man's house [and porch] is his castle."

The vote was 5 to 4. Justice Alito wrote the dissenting opinion, which was joined by Justices Roberts, Kennedy, and Breyer.