It's no secret that conservatives have been out to kill public unions for years. While union membership rates overall have fallen to about 10 percent among workers, public sector union membership remains just over 34 percent. In many ways, the public sector is the one remaining bastion of the American labor movement.

On Wednesday, the Supreme Court stuck the knife in it.

At issue were the fees that unions charge the workers they represent. When a union wins the majority endorsement of the workers in a bargaining unit, national labor law requires it to represent all the workers in the unit, whether they're members or not. The idea is that this sort of exclusive representation encourages labor peace, and stable relations between management and workers. But representing all those workers requires lots of resources, so unions charge those workers fees — including the workers who aren't members.

Conservatives have never been happy with this arrangement. They contend that forcing non-members to pay fees violates their rights. This is what the national push for so-called right-to-work law is all about: Allowing any worker who isn't a member to get out of paying fees.

The problem is, the right-to-work arrangement also means workers get the benefits of union representation for free. And when people can get something for free, they tend to opt out of paying for it. This creates a free-rider problem, draining unions of the resources they need to effectively bargain for better pay, conditions, and benefits. When Michigan did away with mandatory fees in 2012, for example, the loss rate at the Michigan Education Association sped up substantially: Their membership dropped 25 percent in five years, and annual receipts fell 10 percent.

In the Janus v. American Federation of State case that the Supreme Court decided Wednesday, the plaintiffs essentially wanted the Court to apply right-to-work law to all public sector unions.

For decades, the law has been that unions can charge non-members fees to fund their bargaining efforts, but not to fund their political campaigns and issue lobbying. Charging for the latter would violate workers' free speech rights, since it would compel them to fund political speech they hadn't agreed to. But in Janus, union opponents argued that because public workers' wages come from the government, even regular bargaining is inherently political speech. So requiring non-members to pay fees to support those efforts violates their free speech rights.

Justice Samuel Alito, writing for the Court's 5-4 conservative majority, ultimately agreed with this logic.

The immediate effect of Janus will likely be widespread damage to unions across the public sector. Union experts told The New York Times they expect public unions to lose anywhere from a tenth to a third of their members. It will also blow up existing labor arrangements across the country: Twenty states, and thousands of contracts governing public workers, relied on the pre-Janus jurisprudence.

More broadly, this will also be a blow to progressive politics and the Democratic Party. Simply by existing, unions have long provided the nuts-and-bolts organizing that undergirded many liberal policy pushes and Democratic electoral victories. By collapsing the distinction between worker bargaining and political activity, the conservatives on the Court at least implicitly showed their awareness of this. It might seem cynical to suspect that kneecapping the Democrats was the whole point of the Janus case, but no less than President Trump said it out loud: "Big loss for the coffers of the Democrats!" he tweeted shortly after the decision.

Equally telling is the degree to which the Court's conservative majority tied itself into knots to reach the outcome it did. Courts have long struck a balance between workers' free speech rights and the prerogatives of the government as an employer. But the Janus ruling goes much further, interpreting free speech much more aggressively. As Justice Elena Kagan wrote in her dissent, this "creates a significant anomaly — an exception, applying to union fees alone, from the usual rules governing public employees' speech." The one time the Court was willing to invoke a maximalist reading of employees' free speech rights, it also happens to deal a blow to unions.

Interestingly, that maximalist interpretation may also open the door to inventive new labor strategies down the road: If all public worker bargaining efforts are protected free speech, then the multitudinous restrictions on those efforts presumably must go. Unions have also reacted to their shrinking numbers and power by becoming angrier and more engaged, and sometimes more politically effective.

More broadly, the labor peace that Alito nonchalantly dismisses in his opinion was dearly bought: The modern labor movement was birthed by battles between workers and companies in the early 20th century that were astonishing in their scope and violence. Modern labor law sought to broker a deal by placing benefits and limitations on both sides. But as the American right continues to strip out just the pro-union half of that deal, workers may simply decide the deal is no longer worth honoring at all.

For the moment, though, it doesn't look like the conservatives on the Supreme Court are fazed much by any of this. Other than a merciful diversion in the 1960s, the Court has been a reliably reactionary institution throughout American history. At one time, it crushed everything from minimum wages to child labor laws, and the only reason the New Deal survived was because FDR threatened to pack the Court.

Senate Republicans' nihilistic and unprecedented gambit to deny former President Barack Obama a chance to fill an open seat at the end of his tenure, guaranteeing that Justice Antonin Scalia was replaced by another hardline conservative, was an effort to preserve and extend that legacy.

On Wednesday, the Supreme Court's conservatives delivered.