Like ice cream cones and tour buses, the appearance of white chalk marks on the tires of parked cars is a sure sign of summer on the Vineyard. And despite a federal appeals court decision this week that struck down the time-honored law enforcement practice in Michigan, chalking will go on in two out of three down-Island towns.

The U.S Court of Appeals for the sixth circuit ruled Monday that the practice violates Fourth Amendment protections against unreasonable search. In a case brought against the city of Saginaw, Mich., the court found that marking a vehicle’s tire without a warrant qualifies as a search and that the search is unreasonable under the law.

The 10-page decision, written by Judge Bernice Bouie Donald, reversed a district court ruling which had dismissed the case.

Marking vehicle tires is a common practice to enforce time limits on parking in places without meters like Vineyard towns, because it allows officers to cheaply and accurately determine whether a car has moved. Officers mark cars in timed cycles, writing parking tickets if they find the white line in the same place on the car tire when they return.

Police chiefs in the three down-Island towns had varying responses to the federal court ruling.

Jack Collins, who served as chief counsel for the Massachusetts Police Chiefs Association and advises Martha’s Vineyard police, said the ruling does not affect Island law enforcement since it was issued by a federal court in a different circuit. The sixth circuit court of appeals is based in Cincinnati and covers Kentucky, Michigan, Ohio, and Tennessee.

“If it was a first circuit case, that would be different,” Mr. Collins said, referring to the federal appeals court that covers Massachusetts.

Unless and until there is a ruling in Massachusetts, he said, his advice is that Vineyard police chiefs should treat the opinion as advisory.

Edgartown police chief Bruce McNamee said he will follow that advice, and Edgartown special officers will continue to chalk tires this summer.

“Until I hear otherwise, we’ll do the same,” he said.

Officers in Oak Bluffs will also continue chalking, according to Sgt. Michael Marchand. He said the department will take a mixed approach, with some officers using digital devices to track vehicle information.

“It has always been our goal to move to more modern technology such as these devices,” he said. “They’re a little cost prohibitive right now.”

But Tisbury chief Mark Saloio said he will heed the recent ruling.

“They tend to set national precedent,” he said of federal appeals courts. “So until this settles down, I’m going to tell traffic safety officers not to chalk.”

For now, the chief said, officers will use note pads to keep track of vehicles, but he has also been looking into obtaining digital handheld devices.

“If we end up obtaining these devices in the near future, it would essentially make the whole chalking thing a moot point,” he said.

According to data from the Dukes County parking clerk’s office, more than 9,000 parking tickets were entered into the system between June and September last summer. Oak Bluffs had the most tickets and August was the busiest month.

Police chiefs emphasized that parking enforcement is not meant to be a revenue source for the towns.

“From my perspective, it is just a matter of fairness,” Chief Saloio said. “There are a very limited number of parking spaces with a large quantity of vehicles and people. What we’re trying to do is give everybody a reasonable opportunity to visit businesses and not have people monopolize spaces for prolonged period of time.”

Chief McNamee who said he budgets $75,000 for parking and traffic enforcement and would be surprised if the town breaks even with ticket revenue, agreed.

“Parking enforcement is not a revenue creation system. It is to keep a turnover of vehicles,” he said. “There is a quality of life component to keeping that turnover of cars.”

In Oak Bluffs parking enforcement has already begun at the request of the business association, Sergeant Marchand said.

Chief McNamee said he tells summer officers, who are often high school and college students, to refer angry parking ticket recipients to the station and to him.

“I don’t doubt our traffic officers leave here at the end of the summer with a lot of colorful stories about their 10 weeks here in Edgartown writing parking tickets,” the chief said.