With about 20 drug-sniffing dogs gathered in Lawrence for training, the U.S. Supreme Court was considering whether to yank on their leashes.

On Wednesday, the last day of a three-day Kansas Police Dog Assn. training in Lawrence, the court heard arguments in a case that could limit situations in which dogs are allowed to sniff for drugs. The case, Illinois vs. Caballes, is about whether a sniff by a dog is a “search” under the Fourth Amendment, which protects against unreasonable search and seizure.

The case is different from others heard on the subject in recent years, said Sheriff Rick Trapp, a former prosecutor whose agency has the county’s only drug dog. Since the early 1980s, when the Supreme Court held that a sniff by a dog wasn’t technically a search, cases have focused on whether drivers were stopped legally before being sniffed or whether they’d been detained too long waiting for a dog to arrive.

Today, it’s legal to use a drug dog to smell the cars already stopped at a drunken-driving checkpoint — something the county’s German shepherd, Gero, has done in recent months — but not to hold a mere speeder for an unreasonably long time waiting for the dog to come to the scene.

“The law is relatively well-settled right now, and of course the Supreme Court could change all that,” Trapp said.

The Illinois case stems from a traffic stop in which an officer became suspicious and called for a dog to smell the car. The dog arrived quickly and found marijuana in the car, and the driver was sentenced to 12 years in prison, but the Illinois Supreme Court reversed the decision, saying the officer didn’t have enough reason to broaden the stop into a drug investigation.

Lawrence defense attorney John Frydman, a critic of drug prohibition, said he believed a sniff by a drug dog was clearly a search. Even if it’s not as invasive as other methods of searching, it opens the door for further government intrusion.

“I don’t want the government sniffing me,” he said.