The U.S. Court of Appeals for the 6th Circuit, in a first-of-its-kind decision, ruled that marking a car’s tires to gather information is a form of trespass requiring a warrant, similar to police attaching a GPS to a vehicle to track a suspected drug dealer.

Parking attendants across the country have been chalking tires with big white lines for decades in zones without meters to enforce of time limits and issue tickets. It’s a substantial source of revenue for many cities.

The decision, while undoubtedly bringing joy to parking scofflaws everywhere, could cost some cities money, either from lost revenue or having to install meters where none exist.

On the other hand, as Fourth Amendment expert Orin Kerr of the University of Southern California law school tweeted, it “seems easy enough these days for parking enforcers to just take a photo of the car, or even just a close-up photo of the tire, rather than chalk it. . . . No 4A issues then.”