Labor unions can breathe a sigh of relief.

On Tuesday, an equally divided Supreme Court affirmed a lower court's ruling in a case that posed an existential threat to public-sector unionism. As a result of the split decision, the system unions use to collect fees from workers will remain intact.

It's unlikely that unions would have survived the case unscathed had Justice Antonin Scalia not died earlier this year, leaving behind an ideologically split court.

In the case, Friedrichs v. California Teachers Association, a group of California school teachers were challenging the legality of what are known as "fair share" fees. Unions must represent all workers in a bargaining unit — even those who don’t want representation — so where state law allows it, workers can be required to pay fair share fees to help cover the cost of collective bargaining and fund the union.

The teachers argued that the fees violated their First Amendment rights, since, in their eyes, public-sector unionism is inherently political. Had the court taken the opportunity to strike down fair share fees, the entire U.S. public sector would have become akin to a right-to-work zone. Hundreds of thousands of public-sector workers would have then been able to opt out of funding the unions that represent them.

That, in turn, would have dealt a crushing blow to the labor movement in general, which has been increasingly propped up by public-sector unions in recent years, and the Democratic Party it helps fund.

Scalia, in particular, appeared intent on overturning the decades-old precedent upholding the legality of fair share fees. When the justice died in February, it became clear that the Supreme Court could very well deadlock on the Friedrichs case.

In its one-page decision, the court simply said, "The judgment is affirmed by an equally divided Court."