“A man’s home is his castle”—this is not just an aphorism, but a longstanding legal principle. From Biblical times through to the English common law, the home was recognized as a place of refuge in which the owner is protected against uninvited private parties and unjustified government intrusion. That legal shield against arbitrary invasions of the home was embodied in the Fourth Amendment, which resulted in large measure from Americans’ reaction to the British authorities’ use of general warrants to search colonists’ homes without individualized suspicion. As a result of this history, “when it comes to the Fourth Amendment, the home is first among equals.” Florida v. Jardines, 569 U.S. 1, 6 (2013).

In Collins v. Virginia, the issue before the Supreme Court is whether a police officer, uninvited and without a warrant, may enter private property, approach a home, and search a vehicle parked just a few feet from the house. Cato has filed a brief arguing that permitting such a practice would be squarely inconsistent with the Fourth Amendment’s special solicitude for the privacy of the home. At common law, and under the Fourth Amendment, the protection accorded to the home extends to its surrounding grounds and out-buildings—the so-called “curtilage.” Because this area is closely tied to the home, both physically and psychologically, the curtilage is regarded as part of the home itself for Fourth Amendment purposes. This protection is the foremost example of the Fourth Amendment’s general defense against unreasonable government intrusion into private property. Indeed, the text of the Amendment protects “[t]he right of the people to be secure,” not just in their “persons,” but also in their “houses, papers, and effects.”

The general justification for allowing warrantless searches of vehicles is the reduced expectation of privacy in vehicles as they travel on public roads. But there is no such reduced expectation when a vehicle is parked at home. To the contrary, expectations of privacy are at their zenith at the home and its surroundings. And to the extent that the warrantless search of automobiles is justified by their mobility, a vehicle parked at home is immobile; if it leaves the home and curtilage it would become subject to search. Moreover, the existing doctrine on “exigent circumstances” assures that the warrant requirement will not undermine critical law enforcement needs. For example, the need to prevent physical harm or the imminent destruction of evidence would allow officers to intrude on the curtilage without a warrant. But in the absence of those circumstances, the Fourth Amendment’s warrant requirement protects Americans’ most private refuge against the abusive use of government power.