Part of the Washington Examiner's weeklong commentary series on labor unions. To see the entire series, click here.

A lawsuit making its way through federal court in California highlights just how much unions use their right to collect “agency fees” from nonmembers to fund political activities.

When the Supreme Court ruled in 1977 that government employee unions could collect a fee from nonmembers to cover the cost of collective bargaining, the justices noted that such fees could not be used to cover political activities.

In that decision, Abood v. Detroit Board of Education, the court affirmed a Michigan law that required teachers who didn't want to join a union to pay a so-called “agency fee” to the Detroit Federation of Teachers for the work it did representing everyone on the job.

Since then, government unions in 22 states and the District of Columbia have been allowed to collect agency fees, and have largely determined what those fees should be.

That may be about to change.

A lawsuit filed by 10 dissident teachers challenges the California law that requires them to pay $650 each per year to the California Teachers Association and its parent, the National Education Association.

That figure is based on the union's claim that 65 percent of the average $1,000 a year in teachers' union dues go to representing workers.

But the plaintiffs argue that unions are claiming activities which have little to do with representing workers.

The CTA, for instance, has classified its spending on “human rights programs,” including its programs on gay and lesbian issues, as being 100 percent chargeable, meaning that somehow the union believes that these programs are entirely about representing teachers in the workplace.

The CTA also classified a conference on gay-lesbian-bisexual-transgender issues as part of its expenses representing workers, and it attributed 78 percent of the cost of its internal magazine, the California Educator, to be a cost of representing workers, even though the magazine is heavily political.

Meanwhile, the NEA, which receives a portion of money paid by teachers to the CTA, has deemed expenditures for conferences for its staff to be 100 percent chargeable, meaning the entire cost is attributed to worker representation.

In the lawsuit, the teachers contend that the arrangement under California labor law violates their First Amendment rights to free speech and free association because it allows the union to determine the charges.

A teacher can object to the charges, but then he must bear the cost of filing a complaint and backing it up in order to reduce the unions’ assessment.

“These severe infringements on plaintiffs’ rights to free speech and association cannot withstand First Amendment scrutiny,” the suit contends.

“Laws mandating compulsory speech and association must be narrowly tailored to serve a compelling government interest. California’s ‘agency shop’ arrangement cannot meet that standard,” the suit said.

Unions have long made the case that nonmembers who work in a place where collective bargaining is in place are “free riders” if they don’t pay anything toward representation, because they benefit from union work on behalf of its members.

But abuse of the agency fee regime where there does not seem to be a practical constraint on what unions can charge nonmembers has already brought court rebukes.

In 2012, the Supreme Court admonished California SEIU Local 100 for imposing a 25 percent emergency surcharge on nonmembers to support labor's campaign against a series of 2005 initiatives designed to curb government union power in the state.

In that case, SEIU didn’t even bother asking nonmembers if they wanted to opt into the special charges, prompting a solid 7-2 decision by the court against the union’s action.

The court specifically noted in that case that SEIU was also being overly aggressive in deciding what qualifies as a collective bargaining expense.

“The SEIU’s understanding of the breadth of chargeable expenses is so expansive that it is hard to place much reliance on its statistics,” the majority decision held.

“ 'Lobbying the electorate,' which the SEIU claims is chargeable, is nothing more than another term for supporting political causes and candidates," the opinion said.

The issue of agency fees — and the political spending of public sector unions in general — is causing people to question their role more generally.

In a December Field Poll of California residents, 44 percent said government unions do more harm than good, compared with 39 percent who said they did more good.

Even members of union households have become restive. A 2011 Harris Interactive Poll found that 47 percent of those in union households didn’t think union members got their money’s worth from dues, while 62 percent of respondents felt the same way. No wonder those paying the agency fee are now headed to the courts again.

Big Labor increasingly spends money on political activities that have little to do with representing workers. Too often, that spending reflects the attitudes of union leaders, not workers.

In California, the teachers' union contributed $1 million in 2008 to an effort by liberal groups to defeat Proposition 8, which defined marriage as an act between a man and a woman -- an expenditure that had little to do with teacher representation or education.

By contrast, 56 percent of voters in union households supported the initiative, a CNN exit poll showed.

Similarly, when the administration of President George W. Bush began requiring unions to file detailed reports on their giving, the disclosures showed that the NEA donated members' money to advocacy groups that have little to do with worker representation, including Amnesty International and Jesse Jackson's Rainbow PUSH Coalition.

Steven Malanga is a Manhattan Institute senior fellow and senior editor of City Journal.