Are sobriety checkpoints legal?

Yes. The Supreme Court has consistently held that sobriety checkpoints are constitutional. However, law enforcement officers in a sobriety checkpoint cannot stop motorist indiscriminately. In other words, a police officer may pull over every single car, or even every fifth car, but an officer cannot arbitrarily choose who to pull over based on the make or model of a car, the ethnicity of the driver, or a simply hunch (unless, of course, the officer has reasonable suspicion that the driver is intoxicated.)