Bangor, Mich., kindergarten teacher Kimberle Byrd thought that she was no longer a member of the Michigan Education Association. After all, the state had adopted a right-to-work law in late 2012, meaning workers couldn't be forced to join a union even if their workplace was organized. Since she hadn't re-upped her MEA membership after that, she assumed she was out.

So it was a real shock to her when she received a letter in May from a debt collection agency. It said she owed MEA $394.20 in delinquent dues. She was warned to either pay or legally dispute the debt. Otherwise, her credit rating was at stake.

Only then did she learn that MEA requires all members to go through an opt-out process regardless of the right-to-work law. If they don't, the union automatically deems them to have renewed their membership. In addition, the union only allows members to opt out during the month of August — which just happen to be when most teachers are on vacation.

Since Byrd didn't file in August, she is officially still a member as far as MEA is concerned. Another year's dues will cost her around $1,100, she told me.

"They wait until September to start telling you how to pay your dues because they don't want to tell you how to get out. They give you no instructions, no paperwork, no anything prior to September. And at that point, it's too late," she told me. She's still weighing her options, she says.

Laingsburg, Mich., teacher Lisa Jelenek was even blunter: "The local and state MEA representatives intentionally plotted to deceive its members." She's resigned herself to paying for at least another year despite her objections to the union's political agenda.

Byrd and Jelenek's stories highlight a big flaw in Michigan's right-to-work law: Administering it is basically left up to the unions themselves. Big Labor has no incentive to let workers opt out, though, since that means fewer members and less dues money for them. So many unions never bother to inform their members of their rights and make it cumbersome and difficult for those who do try to invoke them.

MEA has been particularly unabashed about this. Nothing in the state law specifies August, for example. That's the union's own rule. As Byrd's letter shows, they will play hardball to enforce it. "MEA believes in the sanctity of contracts -- whether they are with a school district or an individual," then-spokesman Doug Pratt told me last year. A union spokesman could not be reached for comment this time.

As Pratt told the Michigan Senate last December: "The fact is membership organizations like ours don't market how to quit — they market why you should stay."

The conservative Mackinac Center created a webpage to help teachers called

At least Byrd and Jelenek had the opportunity even if they missed it. Others don't even have that.

Battle Creek, Mich., teacher Beth Rayner's union local renegotiated a five-year contract just before the right-to-work law went in effect last year. Doing so ensured the contract would be grandfathered in. As a result, Rayner cannot invoke her rights for at least another four years. In the meantime she'll have to pay the union about $500 annually.

"That's a big chunk of change for a teacher — especially since the five-year contract has no pay raises," Rayner said. She believes her union negotiated away the raises in order to get the school system to renew the contract quickly.

It's not clear how many teachers have been frustrated by these practices but it may be in the thousands. Pratt, now MEA's director of member benefits, told NPR last month that 7,000 of MEA's nearly 148,000 members have not signed up for automatic dues deduction. He attributed this to honest confusion among members over how to pay.

Hmmm. Maybe the union should explain the law more thoroughly to its members.

CORRECTION: This story has been changed to reflect that 7,000 MEA members have not signed up for automatic dues deduction.