An Arizona Superior Court judge ruled that members of a Phoenix law enforcement officers union could not conduct union business while also on the job. The ruling could end, at least in the state, a common practice by organized labor officials that essentially amounts to them getting taxpayer money to run their unions.

In a ruling released Wednesday, Judge Katherine Cooper said that allowing the practice -- called "release time" in the city -- ran afoul of the state constitution's "gift clause," which says the state must prove it receives clear benefits from any payments it gives to a private entity, including unions. Cooper said the unions could not have release time without compensating the city for the lost work hours.

The case was first brought by the conservative Goldwater Institute in 2011 against the Phoenix Law Enforcement Association.

"We hope that this will be the beginning of the end for these practices," Goldwater Institute President Clint Bolick told the Arizona Republic.

PLEA said it would appeal the ruling.

The ruling hinges on a particular clause in the Arizona state constitution, limiting it to that state. But it is still a worrisome sign for unions, since the practice -- known more generally as "official time" -- is common among public sector unions.

"Today's ruling puts government unions everywhere on notice that taxpayers cannot be forced to bankroll union activities," Bolick said.

The rationale behind the practice is that public-sector unions are often limited in what they can do compared to private-sector unions -- police and firefighter unions are typically forbidden from striking, for example -- and official time compensates. Unions negotiate for it in contracts.

Cooper disagreed, ruling that the practice "does not serve a public purpose" and "diverts officers from performing police work."

According to the Arizona Republic: "The city's agreement with PLEA, approved on a split council vote in 2012, authorized the labor group to place six police officers in full-time union roles and set aside 1,800 hours that union officials could give other officers to perform union work. Estimates put the annual cost of the practice at about $850,000."

In a 2011 study, the Goldwater Institute estimated the cost to taxpayers at $3.7 million a year. Some people on the city payroll had not appeared at their regular jobs in over a decade.

A February study by the Office of Personnel Management found that federal employees spent just under 3.4 million hours doing union "official business" on the taxpayer's dime in fiscal 2011, the most recent year for which numbers are available.

Next week, the Washington Examiner will publish a multi-part series by its Watchdog team on official time.