Chief Justice Rehnquist argued that the checkpoints should have been evaluated under the established roadblock framework: weigh the gravity of the public concern, the program’s effectiveness in advancing that concern, and the intrusion on individual liberty. In his view, the checkpoints were brief, standardized, visibly authorized, and conducted without field-officer discretion, making both their objective and subjective intrusions minimal.
He maintained that the program served independently valid public interests because officers checked licenses and registrations and looked for impaired drivers. Sitz approved sobriety checkpoints, and Delaware v. Prouse indicated that neutral roadblocks for license and registration checks could be lawful. The arrests for offenses unrelated to drugs, he argued, confirmed that these interests were genuinely served.
The Chief Justice rejected treating narcotics interdiction as a disqualifying primary purpose. Relying on Whren, he reasoned that once a seizure is objectively justified, the subjective expectations of the officers or policymakers who authorized it should not make the otherwise lawful conduct unconstitutional.
He also emphasized that the dog sniff was not a search under Place and that nothing in the record showed it prolonged the stops. In his view, adding the sniff therefore did not increase the intrusion beyond that of an otherwise valid checkpoint.
Finally, he argued that the majority improperly imported a special-needs, non-law-enforcement-purpose rule from cases involving searches of homes, businesses, or persons. Vehicles receive less Fourth Amendment protection, and brief checkpoint seizures had traditionally been governed by balancing and limits on officer discretion. The new purpose test, he warned, would create uncertainty and litigation over policymakers’ motives without protecting an interest the Fourth Amendment recognizes in this setting.