CHICAGO (CN) – The Illinois Supreme Court vacated a woman’s drug-trafficking conviction, ruling that a police unit operated by an Illinois county state’s attorney’s office, independent from the county’s regular police force, had no authority to make traffic stops.

In 2011, former LaSalle County State’s Attorney Brian Towne formed a police force separate from the county’s police force called the State’s Attorney Felony Enforcement, or SAFE, unit.

SAFE officers were tasked with drug interdiction along interstate highways passing through LaSalle County, just west of Chicago, particularly along I-80, which is the fastest way to get from northern California to Chicago and the big cities of the eastern seaboard.

They arrested dozens of people, and confiscated $1.7 million from drivers before the program was suspended in 2015, according to court records.

Towne’s authority to operate an independent police force became highly controversial, as did his spending of $100,000 of the money collected by the civil forfeitures to fund his own travel to law enforcement conferences, including a $17,000 per diem award for travel expenses.

Cara Ringland was stopped by a SAFE officer because one of her U-Haul’s mud flaps was more than 12 inches off the ground and the officer found it unusual for a woman to be driving a U-Haul alone. A drug dog found 100 pounds of marijuana packed in the back of the van.

She was convicted of drug trafficking, but an Illinois appeals court vacated the charges against her based on its finding that SAFE personnel had no authority to arrest her.

The Illinois Supreme Court upheld that decision Thursday, vacating not only Ringland’s convictions but also those of four men separately charged with felony drug offences in La Salle County. Each defendant was found in possession of a controlled substance after being pulled over by a special investigator with the SAFE unit.

“We hold that the State’s Attorney’s common-law duty to investigate suspected illegal activity did not apply to Towne because he made no showing that law enforcement agencies inadequately dealt with such investigation or that any law enforcement agency asked him for assistance,” Justice Charles Freeman said, writing for the court’s 5-2 majority. “Absent this duty, the conduct of the SAFE unit fell outside of the scope of section 3-9005(b).”

The court voiced concern that the state’s reading of the law would allow the formation of 102 additional police forces in Illinois, each directed by the state’s attorney’s office.

“To construe section 3-9005(b) as the State urges would promote confusion between the distinct functions of general law enforcement and assisting a State’s Attorney in the performance of his or her duties,” Freeman said.

Two justices dissented from the majority opinion.

“There is no support in our common law for restraining the common-law duties of the State’s Attorney based on different types of investigations,” Chief Judge Rita Garman said in the dissent. “Nor is there any support in section 3-9005(b), which spells out the powers of special investigators, for limiting the exercise of peace officer powers based on the request or failure of other agencies.”

The state high court’s decision opens the door for more drivers arrested by SAFE officers to sue.

Alyssa Larson and Jeffrey Straker did just that last month, filing a class action in Chicago federal court against LaSalle County, Towne and John Doe SAFE officers, alleging Towne’s “vigilante police force” violated their civil rights.