The letter ramps up the ongoing legal dispute between labor and Gov. Scott Walker's appointees and brings a new batch of unions into the lawsuit, including those that represent teachers and other government workers statewide.

The move came three days after Dane County Judge Juan Colás ruled the state could not enforce the law against local government unions. Colás declined, however, to issue an injunction against the state in his Tuesday ruling, and a top official with the Wisconsin Employment Relations Commission said then the decision would have no effect on how it operated.

Walker and his fellow Republicans passed a law in 2011 all but eliminating collective bargaining for most public workers. A raft of lawsuits followed over the law, known as Act 10.

Most of the litigation has gone against the unions, but the labor organizations secured a victory last year when Colás sided with Madison Teachers Inc. and a union representing City of Milwaukee employees by ruling the law violated local workers' constitutional rights to free speech, free association and equal protection under the law by capping union workers' raises but not those of their non-union counterparts.

A dispute over that ruling soon erupted over who was subject to the ruling. The state said the decision applied only to the unions that sued, while the unions said it blocked the state from enforcing the law against any unions representing teachers and local government workers. (Both sides agreed the decision did not apply to state employee unions.)

The employment commission continued to enforce Act 10 against unions that weren't part of the lawsuit by requiring them to hold annual elections to maintain their recognition by the state. In response, Madison Teachers Inc. filed a motion asking Colás to enjoin the commission from following Act 10.

In his decision Tuesday, Colás wrote that under his ruling last year the employment commission "may not enforce (Act 10) under any circumstances, against anyone."

But the judge declined to issue an injunction against the state. That's because the state is not enforcing the provisions of Act 10 that have been struck down against the unions that brought the case.

While the state is enforcing Act 10 against other unions, Colás determined he could not issue an injunction because those unions are not parties to the case.

Shortly after the latest decision was issued, the commission's chief legal counsel, Peter Davis, said it would have "no impact" on the commission's plans to hold hundreds of union elections in November.

Stances such as that are what prompted a new group of unions to send their letter Friday. Their attorney, Timothy Hawks, told Chairman James Scott and Commissioner Rodney Pasch that they must immediately halt their enforcement of the law and asked them to do so by the end of the day Monday.

"If you refuse to take such corrective action, we will seek immediately to have you held in contempt of court," Hawks wrote.

Hawks sent the letter on behalf of six unions, including the Wisconsin Education Association Council, the American Federation of Teachers-Wisconsin, the American Federation of State, County and Municipal Employees Council 40 and the Kenosha Education Association. Last week, the commission decertified the Kenosha teachers union in a ruling the union disputes.

The commission's Davis did not comment on the merits of Friday's letter.

Late in the day, the commission scheduled an emergency meeting for Monday to discuss the letter. The three-member commission is appointed by Walker; there is currently one vacancy.

The unions say they could file a contempt motion in the lawsuit even though they are not parties to the case. The law refers to motions for contempt being filed by "a person aggrieved" rather than a party to a case.

Department of Justice spokeswoman Dana Brueck issued a brief statement questioning why the letter was sent.

"We're not sure why they sent this letter," Brueck's statement said. "They tried for an injunction, and the judge didn't grant it."

Lester Pines, the attorney for Madison Teachers Inc., said the commissioners' behavior was the most contemptuous he had ever seen.

"They are public officials who took an oath to uphold the Wisconsin Constitution and the U.S. Constitution and they are thumbing their nose at a court order," he said.

"The reason they are ignoring the court order — deliberately ignoring the court order, thumbing their nose at the court — is because they want these unions decertified."

Even before the latest round of wrangling, the underlying case was already headed to the state Supreme Court. The high court agreed to take the case in June but has not yet scheduled oral arguments.

The unions have seen defeat in other cases in circuit court and federal court.