Wisconsin License Plate Reader Laws

Status at a glance

No ALPR statute

Wisconsin has no statute that regulates license plate readers. Its sources are narrow: one appellate case about GPS tracking, which isn’t an ALPR case, and one county sheriff’s policy. Wisconsin bills use the term “registration plate reader.” Three 2025 bills on the subject appear on the Legislature’s site, and each shows “Failed to pass pursuant to Senate Joint Resolution 1” on 3/23/2026.

• AB 883, “limiting the use of automatic registration plate readers.”
• AB 576, “limiting the use of automatic registration plate readers, requiring a search warrant for data from an automatic registration plate reader or security camera, and providing a penalty.”
• SB 299, “a grant program for the purchase of automated registration plate reader systems.”

None is law, so this page doesn’t describe what they would have required.

State v. Brereton: GPS, not ALPR

State v. Brereton, 2011 WI App 127, is a published Court of Appeals decision filed August 10, 2011. It isn’t an ALPR case. Police stopped Brereton’s car, had it towed to an impound lot, got a warrant, and installed a GPS tracking device under the hood. Brereton appealed “the denial of his motion to suppress evidence obtained through use of a Global Positioning System (GPS) tracking device.”

The court affirmed “because the police did have probable cause to seize the vehicle and then the GPS device was placed pursuant to a lawful warrant.” Along the way it described an earlier Wisconsin holding that “no Fourth Amendment search or seizure occurs when police attach a GPS device to the outside of a vehicle while it is in a place accessible to the public.”

That earlier holding predates United States v. Jones (2012), in which the U.S. Supreme Court addressed GPS tracking under the Fourth Amendment. It shouldn’t be read as current federal law. The Wisconsin Supreme Court later reviewed Brereton (2013 WI 17); we didn’t retrieve that decision. Brereton is listed here only as the nearest Wisconsin appellate case on vehicle-location surveillance. See is ALPR a search? and the mosaic theory.

One agency’s policy: Dane County Sheriff

Dane County Sheriff’s Office Field Services Manual § 405.19 covers the office’s Flock ALPR system. Its history shows a revision on 9/10/25. It is one agency’s policy, not a statute. Other Wisconsin agencies may follow different rules.

• Use. The system is restricted to “legitimate law enforcement uses.” Employees may access stored data on a reasonable belief that it relates to a specific official action or investigation.
• Retention. “ALPR data in the FLOCK system is stored for 30 days,” after which it is automatically removed. The investigating deputy or detective must download images needed as evidence.
• Sharing. If an outside law enforcement agency asks for a search, it must be documented with the officer’s name, agency and case number.
• Alerts. Before acting, deputies verify that the plate matches the plate the system ran and check the plate’s current status through dispatch or query.
• Audits. The Captain of Field Services must ensure an audit of Flock browsing inquiries “at least once during each calendar year.”

See ALPR data retention and sharing.

What this can mean in a Wisconsin case

• Which agency’s cameras captured the data, and what does its written policy say about retention and access?
• For Dane County data, was it downloaded within 30 days, and does the record show the access was tied to a specific investigation?
• If another agency requested a search, was it documented with a name, agency and case number?
• For a stop on an alert, was the plate verified first? See ALPR alert traffic stops.
• How do post-Jones federal cases bear on the ALPR use, given that Brereton came earlier?