Sometime during the next few months, the US Supreme Court will issue a decision that could profoundly weaken public employee unions across the country.

By all accounts, the justices -- in the oral argument in Friedrichs v. California Teachers Association -- signaled that they are poised to rule that workers' payment of dues to public sector unions must be voluntary. Specifically, the Court is expected to strike down, on First Amendment grounds, state laws requiring payment of dues (or an equivalent amount) by public sector workers who choose not to join the union.

A majority of the Court appears persuaded that such arrangements -- requiring workers to support union advocacy of positions with which they may disagree -- constitute "coerced speech" in violation of the First Amendment. The Court's prior cases have permitted these arrangements as necessary to pay for collective bargaining activities, benefiting union members and nonmembers alike, subject to the proviso that nonmembers must be able to obtain a refund for overtly political activities, like lobbying and campaign contributions.

The public employees in the Friedrich case -- teachers in Los Angeles public schools -- argue that collective bargaining between unions and the government is no less political than campaign contributions or lobbying. When public sector unions bargain with a state or local government agency over pensions, health insurance, average class size, or the length of the school year -- these are all inherently political issues that directly implicate the interests of voters, not just "management" in the traditional sense.

The Court appears ready to buy this argument.

The practical implications of this change are huge. The political clout of unions in the public sector is a function of their ability, among politicians, to reward their friends and hurt their enemies. In a world in which dues payments collapse because workers can't be forced to pay them, public sector unions will find they have few friends, while their enemies can defy them with impunity. In states like California, where public employee unions have long held sway, both in the Legislature and in city councils and school boards across the state, the balance of political power will shift away from teachers, police and bureaucrats.

From a political standpoint, I am generally in favor of this shift. Disproportionate power in the hands of a special interest group, like public sector unions, is fundamentally anti-democratic. And the acquisition of that power through campaign contributions, though legal, is inherently corrupting of the political process. Nonetheless, I think the constitutional arguments against mandatory union dues in the Friedrich case are misconceived.

The essence of the coerced speech doctrine, established in Supreme Court decisions going back three decades, is that government may not force citizens to subsidize the advocacy of a policy or point of view with which they disagree. The idea is that forced support for, or association with, a point of view that you dislike is the flip side of censorship: the silencing of your expression of a point of view that the government dislikes.

But this First Amendment principle is subject to a big exception. If the objectionable speech that you are being forced to support or subsidize is government speech, then the First Amendment is not implicated, much less transgressed. This is the holding of Walker v. Texas, a 2015 Supreme Court case involving state screening of drivers' requests for specialty license plates. Texas' rejection of a license featuring a Confederate flag did not infringe free speech rights, the Court ruled, because specialty licenses are government speech.

The government speech exception presumably also explains why the First Amendment doesn't stand in the way of the levying of taxes. Every April 15, Americans are required to pay income taxes, some portion of which subsidizes or supports policies (and their advocacy) with which many taxpayers disagree. Those taxpayers, however, may not invoke the First Amendment to withhold a portion of their taxes. The reason: the speech to which they object is government speech.

The problem is that the distinction between government coercion of private speech (triggering First Amendment scrutiny) and government coercion of its own speech (exempt from First Amendment scrutiny) is not at all clear. Indeed, one could characterize the union speech in the Friedrich case is governmental because it is approved by government, a point that Supreme Court Justice Sotomayor tried to make during oral argument.

Moreover, the characterization of speech as governmental hardly removes the constitutional sting of the coercion. On the contrary, being forced to subsidize an idea with which one disagrees is even more objectionable, from a First Amendment standpoint, if the idea is expressed in the government's words than in the words of a private speaker.

A decision by the Court that diminishes the resources -- and therefore the influence -- of public sector unions would effect a major realignment of political power at the state and local level. While that would be a welcome development politically speaking, the Court appears ready to embrace a legal theory whose arbitrariness could undermine free speech rights in future cases.

Peter Scheer, a lawyer and journalist, is executive director of the First Amendment Coalition. This article does not necessarily reflect the views of FAC's Board of Directors.