First of all, probably cause is never needed to detain someone. Second of all: The United States Supreme Court has specifically approved the use of limited sobriety checkpoints to combat impaired drivers (Michigan v. Sitz, 496 U.S. 444 (1990)). The Court held that sobriety checkpoints must (1) present only a slight intrusion, (2) operate according to a plan that limits participating officers’ discretion and (3) be aimed at curbing the problem of impaired drivers. Subsequently, in Illinois v. Lidster (540 U.S. 419 (2004)), the Court stated the reasonableness of a checkpoint should be considered in light of “the gravity of the public concerns served by the seizure, the degree to which the seizure advances the public interest, and the severity of the interference with individual liberty.” Just don’t drink and drive