Are so-called “right-to-work” laws the equivalent of slavery? That’s one argument Big Labor is making to try to counter them. Their case is an absurd stretch, but nevertheless worth looking at because it serves as a good primer on what these laws actually do.

Right-to-work laws prohibit individual workers from being required to either join a union or pay dues to one as a condition of employment. In other words, without right-to-work laws, if you want a job at a unionized workplace, you have to support its union.

The point is that the individual gets to decide whether they want to join or not. Unions are perfectly legal in right-to-work states, they just have to be exclusively voluntary organizations.

The catch here is that most union contracts with management guarantee that they are the "sole bargaining representative" for employees. So when workers drop out, legally only the union can represent them in matters with their employer.

This is the crux of the union’s slavery argument: Right-to-work laws put them in the position of having to provide union services for free to nonmembers.

In a Dec. 6 circuit court filing, Detroit-based Teamsters Local 214 argued that it should be allowed to charge four former members $150 apiece to file a grievance against their employer. Otherwise this would constitute a “violation of the prohibitions against involuntary servitude in that members of Local 214 are being required to provide the benefit of their work against their will in service of the plaintiffs.”

In other words, you cannot allow these people to freeload off of us.

International Union of Operating Engineers Local 150 made the same argument in an April 2012 court challenge to Indiana’s newly-adopted right-to-work law. (The case was dismissed in January.)

It argued that the law required “unions to furnish services to all persons in bargaining units that it represents, but it may not require payment for those services” in violation of the 13th Amendment.

Putting aside the bad taste of the unions comparing their situation to that of slaves, they do seem to have a point: Why shouldn’t they be able to demand payment for services?

The catch here for people like the Detroit ex-Teamsters is that they have no other option. Because the union is the sole bargaining agent, they claim they can't file complaints on their own – they can only file their grievances through the union and the union waives these fees for members. In other words, they were being punished for having left the union. (Local 214 generally denied all of these allegations in their court filing)

How do unions become the sole bargaining representative in the first place? Because they demand it during their contract negotiations with management. But nothing prevents unions from negotiating “members-only” contracts in which they only represent people who voluntarily join the union.

They just do not like to do this because being the sole employee representative is a powerful tool to keep employees on board and other unions out.

So is it slavery if the unions push for contracts that put them in this position should a state adopt a right-to-work law? The obvious answer is no. They have only themselves to blame for this situation.

Nevertheless, expect to hear this argument again in the future because right-to-work laws are making a comeback. A total of 24 states have versions of them now and efforts to adopt them are being made in traditionally union-friendly states like Ohio and Pennsylvania too.

The odds are long, but not impossible. Who would have thought just a few years ago that Michigan would ever join the list? Union leaders would be well advised to come up with a better argument against the laws.