Fourth Amendment advocates scored a victory today when the U.S. Supreme Court ruled 8-1 against a warrantless police search that involved an officer entering private property for the purpose of examining a motorcycle stored under a tarp in the driveway near a home. "In physically intruding on the curtilage of [Ryan Austin] Collins' home to search the motorcycle," Justice Sonia Sotomayor wrote for the majority in Collins v. Virginia, the officer "not only invaded Collins' Fourth Amendment interest in the item searched, i.e., the motorcycle, but also invaded Collins' Fourth Amendment interest in the curtilage of his home."

The central question before the Supreme Court in Collins v. Virginia was whether the so-called automobile exception to the Fourth Amendment, which allows the police certain latitude to search vehicles on public streets without a warrant, also allows the police to walk up a driveway without a warrant and search a vehicle parked in the area near a house. The Court ruled 8-1 that the automobile exception should not apply in this scenario.

"To allow an officer to rely on the automobile exception to gain entry to a house or its curtilage for the purpose of conducting a vehicle search would unmoor the exception from its justifications, render hollow the Fourth Amendment protection the Constitution extends to the house and its curtilage, and transform what was meant to be an exception into a tool with far broader application," wrote Justice Sotomayor. "Indeed, its name alone should make all this clear enough: It is, after all, an exception for automobiles."

The sole dissent in the case was filed by Justice Samuel Alito, who insisted that the police had every right to engage in this sort of warrantless activity. "The Fourth Amendment prohibits 'unreasonable' searches," Justice Alito maintained. "What the police did in this case was entirely reasonable. The Court's decision is not."

This clash over the meaning of the Fourth Amendment should come as little surprise. Since joining the Supreme Court in 2009, Justice Sotomayor has distinguished herself as both a leading critic of police misconduct and an outspoken advocate of Fourth Amendment rights. Justice Alito, by contrast, has emerged as perhaps the Court's most dependable voice in support of law enforcement in such cases.

Today's decision will not be the last time that Sotomayor and Alito stand on opposite sides of a Fourth Amendment dispute.