David L. McColgin [Supervisory Assistant Federal Defender (Appeals), Federal Community Defender Office for the Eastern District of Pennsylvania]: "Arizona v. Gant [PDF file] is one of the most significant pro-Fourth Amendment decisions in decades. Overturning the settled law in federal and most state courts, the Supreme Court ruled that police may no longer automatically search the passenger compartment of a car incident to the arrest of one of the car's occupants. Instead, police may search the passenger compartment only if the arrestee is unsecured and "within reaching distance of the vehicle," or if "it is reasonable to believe the car contains evidence of the offense of arrest." In so ruling, the Court reaffirmed that people do have a Fourth Amendment privacy interest in the contents of their cars.

Gant is big news because it reverses the trend toward limiting Fourth Amendment privacy interests when a search involves a vehicle. Four decades ago, in Chimel v. California, the Supreme Court ruled that police may search incident to arrest only the area within the arrestee's "immediate control" – the area within which the person could grab a weapon or evidence. But in New York v. Belton, the Court carved out a large exception from this rule for car stops, holding that police could always search the passenger compartment of a car incident to the arrest of an occupant. This ruling was based on the notion that any privacy interest in the contents of a car is at best a limited one.

Belton's bright-line rule completely untethered car searches from the reasoning of Chimel. Police across the country were trained that upon arresting the occupant of a car, they could place the arrestee handcuffed inside a police car, and then conduct a full-scale search of the passenger compartment, even though the arrestee could not possibly reach anything inside the car that was stopped. Recently, the Court broadened the Belton rule in Thornton v. United States, applying the rule even when the arrestee had already walked away from the car.

Justice Stevens' majority opinion in Gant restores the privacy interests motorists have in their vehicles under the Fourth Amendment. While noting that the privacy interest in a car is less than that in a home, Gant makes clear that the former is "nonetheless deserving of constitutional protection," especially since the searches authorized by Belton included personal effects such as purses and briefcases in the passenger compartment. The "central concern underlying the Fourth Amendment," Justice Stevens explains, is "the concern about giving police officers unbridled discretion to rummage at will among a person's private effects."

Although Justice Stevens asserts that the Court has not actually reversed Belton and Thornton and only narrowed their scope, Justice Alito's view in dissent is more accurate. As Justice Alito writes, "there can be no doubt" that Gant overrules both decisions. Police across the country now will have to be retrained that they can search the passenger compartment of a car only if (1) the arrestee is uncuffed and within reaching distance of the car, or (2) the police have reason to believe there is evidence of the offense of arrest in the car.
The most curious aspect of Gant is the inclusion of the second ground for a search. As Justice Stevens himself notes, this second ground actually has nothing to do with the rule of Chimel (which is encapsulated in the first ground). Instead, it appears to have been added so as to bring in Justice Scalia's fifth vote to make a majority. Only Justice Scalia is an advocate for this ground. As he explains in his concurrence, although he disagrees with the first ground and the application of Chimel to car searches, with the addition of the second ground he joined the majority to avoid a 4-1-4 split decision. This leaves the second ground with little support on the Court, and virtually no definition. It is unclear exactly what standard police must meet in order to have "reason to believe" that evidence of the offense of arrest will be found in the car. Is this standard somewhere in between "reasonable suspicion" and "probable cause?" Only time (and lots of litigation) will tell."