In less than three years, four historically union-friendly Midwestern states have adopted laws that threaten to speed the decline of union membership. That has Big Labor's lawyers scouring their libraries for something -- anything -- that can stem this tide.

They've claimed these "right to work" laws violate the First Amendment, the equal protection clause and even anti-slavery laws. Little seems to have worked so far.

In an appeal filed last week in Indiana, union lawyers even argued the laws themselves are unconstitutional ... under the very same federal law that explicitly allows them.

"It's pretty much a desperation move on their part," said Glenn Spencer, vice president of the Chamber of Commerce's Workforce Freedom Initiative.

The four cases show how ill-prepared Big Labor is to fight right-to-work laws. Even top leaders struggle to debate the issue.

Right-to-work laws allow states to prohibit union contracts that require all employees to belong to a union or at least pay dues to one. In other words, they prevent workers from being forced to support a union.

Twenty-four states currently have these laws. Of those, 19 adopted them between 1943 and 1963. These were mostly southern or rural states without strong union traditions. Only two states, Idaho and Oklahoma, adopted versions in the three decades prior to 2011.

So it was reasonable to assume by then, most states open to it had already adopted it. Most labor leaders have never had to seriously engage the issue until now.

Right to work roared back in 2011, when Ohio and Wisconsin passed versions limited to government employees (Ohio's was subsequently overturned by a ballot initiative). Indiana passed right to work in 2012, and Michigan followed later that year.

When I had the opportunity to interview American Federation of Teachers President Randi Weingarten about them via Twitter earlier this year, she simply refused to answer whether it should be an individual's right to decide whether he or she pays union dues.

The right-to-work laws are an existential threat for Big Labor. Wisconsin's public-sector unions, for example, have lost between a third and a half of their members in just two years. They're now throwing out every argument and hoping something sticks.

International Union of Operating Engineers Local 150 members actually claimed Indiana's law violated the 13th Amendment, which outlaws slavery. Not getting union dues from nonmembers amounted to "involuntary servitude," they said, since union contracts require them to represent all workers.

The union appealed late last month, arguing the law violated free speech rights by denying it dues from nonmembers. This argument meant pushing the "money equals speech" argument that liberal groups have scorned in the campaign finance reform debate.

Local 150 also argued that federal labor law doesn't allow right-to-work laws -- contrary to 50 years of law and litigation. Courts haven't bought any of this so far.

Big Labor has struggled with similar legal challenges in Wisconsin. Some judges have overturned or stayed the law only to have the state Supreme Court and federal courts uphold it.

Unions are also pursuing an equal protection clause argument because the law exempts police and firefighter unions but not others. But laws have long made exceptions for emergency services.

Meanwhile, American Civil Liberties Union lawyers argue Michigan lawmakers violated the state's open meeting law when they passed the bill. The room was closed because it was overflowing and police feared structural collapse. "You have a real uphill battle, frankly," the judge told ACLU lawyers in April.

That's the best hope the unions have for a victory right now, and it involves a technical violation of state procedure and not the law itself.

They don't seem to have any broader strategy. That doesn't bode well for Big Labor. If the economies do well in Indiana, Wisconsin and Michigan -- they can hardly do worse in the latter -- other states might be tempted to adopt the laws, too.

Sean Higgins ( is a senior editorial writer for The Washington Examiner. Follow him on Twitter at @seanghiggins.