Michigan labor unions are understandably upset over the Wolverine State's adoption of a right-to-work law and are fighting it in every way they can. Detroit-based Teamsters Local 214 has gone so far as to argue that it violates anti-slavery laws. Yes, anti-slavery.

In a Dec. 6 court filing, Local 214 argued that right-to-work laws are "a violation of the prohibitions against involuntary servitude" citing Article I, Section 9 of the state constitution: "Neither slavery, nor involuntary servitude unless for the punishment of crime, shall ever be tolerated in this state."

"The claim was made in response to a lawsuit filed by four City of Dearborn employees who were going to be charged $150 by the union for any grievance they filed after they left the union when they exercised their rights under state law," according to a blog posting by the conservative Mackinac Center.

A Local 214 official could not be reached for comment by the Washington Examiner.

Right-to-work laws prevent workers from being required to either join a union or pay dues to one as a condition of employment. In cases where workers do opt out they are often still required to go through the union to file any grievance with their employers. Local 214 has argued that requiring them to do this without charging the non-union workers a fee for the effort is, in effect, slavery because otherwise they would be forced to do the work without pay.

That sounds reasonable enough but it ignores why the non-union workers must go through the union in the first place: The union's contract with management guarantees that it will be the sole employee representative. That is something unions typically demand during their negotiations with management. But nothing prevents them from negotiating "members-only" contracts under which they only represent their own members.

This is nevertheless a popular talking point with unions, so expect to hear it again in the future. For more on the issue, see my June column.