A deeply divided Illinois Supreme Court ruled Thursday that police may use drug-sniffing dogs to inspect cars during traffic stops, even if they have no particular reason to suspect the driver of illegal activity.

The 4-3 ruling comes in a case that went all the way to the U.S. Supreme Court.

Originally, the Illinois courts ruled that the search was improper, but that was overturned by the federal court, and the case was sent back to Illinois for further hearings.

The case involves Roy Caballes, who was stopped by Illinois police in 1998 for driving 6 mph over the speed limit. Although Caballes lawfully produced his driver's license, troopers brought over a drug dog after noticing air freshener in the car and noting Caballes appeared nervous.

The dog indicated drugs were in the trunk, and police searched it even though Caballes refused to give permission. They found $250,000 worth of marijuana, and Caballes was convicted of drug trafficking.

Initially, the verdict was thrown out by the Illinois Supreme Court, which ruled the search was improper because police had no particular reason to suspect Caballes had drugs. But the U.S. Supreme Court found that a dog sniffing the outside of a car did not amount to an improper search.

Caballes challenged his conviction again by arguing that the Illinois Constitution's privacy protections are stronger than those in the U.S. Constitution.

This time, the Illinois court upheld the search, although Justices Charles Freeman, Mary Ann McMorrow and Thomas Kilbride dissented.

"It's truly an erosion of our Fourth Amendment rights," said Caballes' lawyer, Ralph Meczyk, who was still studying the ruling and didn't know if he would appeal.