The city of Minneapolis can't break up its police union into separate entities for rank-and-file officers and higher-ranking supervisors — a move the mayor has advocated for since his first term — according to a ruling published Thursday by the state's Bureau of Mediation Services.

Under the current structure of the Police Officers Federation, sergeants and lieutenants are in the same bargaining unit as patrol officers. In 2018, shortly after taking office, Mayor Jacob Frey said that this model makes supervisors less likely to discipline officers who are on their "team" and that creating separate unions would put Minneapolis in line with other U.S. cities.

In its petition to the state for the authority to break the union into two, the city argued that the supervisors and rank-and-file officers "represent fundamentally different roles, responsibilities, and interests, and should no longer be in the same bargaining unit."

The police federation opposed changing the structure. An attorney for the union argued that sergeants and lieutenants don't meet the definition of "supervisor" under state statutes, so the change is not justified.

Siding with the federation, the Bureau of Mediation Services found "no cause to declare the existing unit not appropriate."

"The City's main argument for exclusion of the Police Sergeant and Police Lieutenant from the existing unit is for perceived managerial role influence issues," reads the decision, signed by Bureau of Mediation Services Commissioner Johnny Villarreal and a hearing panel. "They have not proven this to be necessary by a preponderance of the evidence."

Frey said he was disappointed with the decision.

"We've been working on this for four years and I was hopeful the state would grant us this change," he said. "To be clear, we can still do the work that needs to be done — it's just something else we've got to account for."

Frey said he would consult with the City Attorney's Office on whether there's another legal avenue to pursue the change.

Frey isn't the first elected official to clash with the Minneapolis Police Officers Union. In 2014, in a KSTP-TV report, police union President John Delmonico accused Mayor Betsy Hodges of "flashing gang signs" with a man in a photograph. The accusation backfired and attracted international mockery, in an episode dubbed "Pointergate," when video emerged showing that Hodges and the man were only pointing at each other during a voter drive.

After the murder of George Floyd by a Minneapolis officer, Delmonico's successor, Bob Kroll, sent a letter to rank-and-file officers condemning the "despicable" response to rioting by Frey and Gov. Tim Walz. Kroll also described what would be a failed attempt to reverse Frey's termination of the officers who detained Floyd.

The letter elicited criticism from city officials, including former Police Chief Janeé Harteau, who called Kroll "a disgrace to the badge."

Kroll has since retired. Earlier this year, he was banned from policing in three metro counties as part of a settlement over a pair of lawsuits that accused Minneapolis police of unconstitutional brutality in response to demonstrations following the killing of Floyd.

Frey and other elected officials have publicly criticized the union for thwarting attempts to reform the Minneapolis Police Department. After Floyd's murder, former Chief Medaria Arradondo temporarily stepped away from contracting negotiations with the union.

In an interview Thursday, Frey said splitting up the federation would have made it easy for supervisors to discipline rank-and-file officers when they break the rules.

"You're less likely to hold somebody accountable that is a member of the same team," he said. "That's not a police thing; that's human nature. And so this was a move for accountability. This was a move to reflect the rank and responsibility of the members."

For its part, the union has dismissed the city's attempts as a futile waste of taxpayer money. "I think you'd be hard-pressed to find anybody who can give you an example of a situation in which an employee got preferential treatment because of their union affiliation," union attorney Jim Michels told the Star Tribune in 2018.

Union leadership did not immediately comment on the ruling.