Enforcement

DUI Checkpoints: What Police May and May Not Do

What Sitz actually held

The case that made checkpoints possible is Michigan Dept. of State Police v. Sitz, 496 U.S. 444 (1990). The Court did not say that stopping a car without suspicion is fine. It said that a brief, standardized stop at a fixed checkpoint is a seizure under the Fourth Amendment, and then weighed the state’s interest in stopping impaired driving against the intrusion on the driver.

That balancing is what the rules below come from. Each one exists to keep the intrusion small and to remove the officer’s discretion about whom to stop — because discretion is exactly what the Fourth Amendment is suspicious of.

The four things that make a checkpoint lawful

• Supervisory planning. The decision about where and when is made by command staff in advance, not by the officers working the line.
• A neutral formula. Every car, or every third car, or every car in a designated lane. What cannot happen is an officer choosing cars by look.
• Advance notice. Most states require publication — a press release, a posting, signage on the approach.
• Brief detention. The initial stop is a short conversation. Anything longer needs its own justification that arose during the stop.

A checkpoint that fails one of these is not automatically thrown out, but the failure is the argument. It is also the reason checkpoint cases turn on records rather than on what the driver remembers: the plan, the formula and the notice either exist on paper or they do not.

Where checkpoints are not allowed at all

Twelve states do not permit sobriety checkpoints. Some read their own state constitution as more protective than the Fourth Amendment; others simply never passed enabling legislation. The list has been stable for years but it is a state-law question, so it is the one item on this page most worth re-checking against your own state before relying on it.

The twelve are Alaska, Idaho, Iowa, Michigan, Minnesota, Montana, Oregon, Rhode Island, Texas, Washington, Wisconsin and Wyoming — but they arrive there by four different routes, and the route matters if you are reading a case.

• State constitution. Michigan, Oregon, Rhode Island and Washington read their own constitutions as more protective than the Fourth Amendment. Michigan is the striking one: it lost Sitz at the Supreme Court, then on remand its own high court held the checkpoint invalid under the Michigan constitution anyway.
• Case law on other grounds. Idaho, Iowa and Minnesota.
• Statute. Wisconsin and Wyoming legislated against them.
• No authorizing law at all. Alaska and Montana simply never enabled them. Texas reached the same result through its own reading of federal constitutional law rather than a state ban.

Three more states allow checkpoints only with prior judicial approval: New Hampshire, South Carolina and Utah.

As of December 2025, 37 states and the District of Columbia permit and run them. This is state law and it moves — check your own state before relying on the list.

Turning away

Drivers ask whether avoiding a checkpoint is itself grounds to be stopped. In most states the answer is no, provided the turn is legal — a lawful turn at a lawful place. What creates suspicion is the unlawful part: an illegal U-turn, crossing a solid line, pulling into a closed lot. The avoidance is not the problem; the traffic violation used to accomplish it is.

What this means for a case

Checkpoint challenges are documentary. They ask for the operational plan, the formula, the notice and the supervisor’s authorisation, and they compare those against what happened. That is a different exercise from contesting a roadside stop based on observed driving, and it is worth knowing which of the two your case is before anything else.

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