By David Eggert, The Associated Press

LANSING — Michigan's largest teachers' union should allow members to resign at any time and stop enforcing an annual one-month opt-out window, a state labor judge ruled, relying on the state's right-to-work law that took effect last year.

The administrative law judge, Julia Stern, recommended Tuesday that the Republican-controlled Employment Relations Commission order the Michigan Education Association to no longer limit school employees to leaving the union in August. She said the right-to-work law incorporated a federal law interpreted to give public employees the ability to leave their union anytime.

The state's largest public sector union said Thursday that fewer than 5,000 of 110,000, or 5 percent, of active members opted out last month. Opponents countered that roughly 50,000 had no incentive to leave because they still have to pay fees for bargaining and other services — even if they decide not to belong and pay full dues — until their labor contracts lapse. The union said the 50,000 figure is high.

Chuck Alberts, president of the Lansing Schools Education Association, took aim at what he called "anti-teacher union groups" - including the Mackinac Center, Americans for Prosperity and the National Right to Work Coalition - saying student needs are not their priority.

"Think of all the millions of dollars that have been spent against teachers being union members," Alberts said. "Imagine if that had been spent on educating the future leaders of Michigan.I challenge them to put students first like the teachers of Michigan do everyday."

It wasn't immediately clear how many local teachers had opted out.

The legal decision and the union's decision to make public its latest membership figures followed an intense month of lobbying by organized labor and pro-business groups to persuade teachers to leave or stay, in the first real test of the law that no longer allows forced union fees as a condition of employment.

Lawyers on both sides learned of Stern's decision Wednesday night.

"Judge Stern's ruling goes along with our belief that teachers are professionals and not piggybanks for the MEA," said Patrick Wright, director of the Mackinac Center Legal Foundation.

Steven Cook, the union's president, said its members believe in the union and public education, and "no amount of outside rhetoric is going to dissuade them."

An appeal is planned, first with the commission — controlled 2-1 by Republicans — and then likely the state appeals court and ultimately the Michigan Supreme Court.

"We probably have a couple years more of this to go," Wright said.

The union's general counsel, Michael Shoudy, said the resignation process has been in place for more than 40 years.

"We remain hopeful that MERC will find the August window to be consistent with the law," he said.

Michelle Kaminski, an associate professor at Michigan State University's School of Human Resources & Labor Relations, said the ruling "definitely goes contrary to established labor law in the private sector." She said opt-out windows had been protected by the National Labor Relations Board because unions need to know membership levels to manage their finances.

A significant number of dropouts over time would deliver a financial blow to the influential union. Members pay up to $640 annually to the state union and $182 to the National Education Association, along with local dues.

The ruling directly affects seven employees in four school districts — Saginaw, Battle Creek, Grand Blanc and Standish-Sterling — who complained they were unable to drop their membership after missing the August window in 2013. If the decision stands, it could have broader implications for other unions with time restrictions on dropping out.

The Mackinac Center Legal Foundation and the National Right to Work Legal Defense Foundation filed lawsuits and labor complaints on behalf of the teachers, accusing the union of not publicizing the opt-out period and threatening to send members who unsuccessfully tried to leave in other months to collections for not paying their dues.

Union leaders have defended the union, saying the job of a membership association is not to help people resign and contending that the annual monthlong window is essential for planning and budgeting.

The judge agreed with the reasoning for the window but said the law changed with the passage of the right-to-work measure. Stern dismissed allegations that the union violated state labor law by trying to send members to collections for not paying dues. She also said unions have no duty to educate their members about the right-to-work changes.

About 8,000 members stopped paying dues last school year after another Republican-written law, which ended automatic dues deductions from school employees' paychecks, took effect. The union said several thousand have resumed paying dues.

In the past two years, Republican-controlled legislatures in Michigan and Indiana have passed laws making union fees voluntary, and other Midwestern states are considering the idea.

Lansing State Journal reporter Justin A. Hinkley contributed to this report.