ON JANUARY 11th Rebecca Friedrichs, a California teacher challenging the way public-sector unions do business, bounded out of the Supreme Court wearing a big smile. Ms Friedrichs’s lawyer, Michael Carvin, had just argued her case in front of nine justices, five of whom gave her complaint a warm reception. But whilst Mr Carvin and Ms Friedrichs were celebrating beside the fountain on the Supreme Court plaza, they had no inkling that one of the expected votes in their favour would disappear with Antonin Scalia’s death in February, or that a court split down the middle would thwart their long-sought victory a month later.

It takes a majority of justices to overturn a lower-court ruling. So on March 29th, when the now eight-member Supreme Court released a terse, one-sentence decision in Friedrichs v California Teachers Association, it made all the difference that the ninth circuit court of appeals had turned back the challenge to the unions when it considered Ms Friedrichs’s case last year. That decision, the justices wrote in an unsigned ruling, “is affirmed by an equally divided court”. A near-certain blow to teachers, police and firemen’s unions in about half the country was averted by a vote of 4-4.

Ms Friedrichs’s target was a nearly four-decade precedent upholding state laws that allow unions to collect “fair-share” fees from public-sector employees who opt not to sign on as members. In Abood v Detroit Board of Education, decided in 1977, the court held that since non-members are represented by unions and profit from their efforts, fair-share or “agency” fees help preserve “labour peace” and prevent workers from free-riding on their dues-paying colleagues. Unions may not force non-members to pay for their overtly political activities (like campaigning for particular candidates), Abood said, but it is fine for states to conclude that the cost of bread-and-butter negotiations over salaries and benefits should be shared by everybody benefiting from those endeavours.

Ms Friedrichs and a handful of other teachers challenged this distinction. Discussions about worker compensation and policies like class size, they claimed, address core political issues. By forcing every teacher to write a cheque to the union each month, the plaintiffs contended, the agency-fee regime compels dissenters to support ideas they reject, violating their freedom of speech.

Four years ago Justice Samuel Alito called Abood “something of an anomaly”, all but inviting a Supreme Court challenge, and the libertarian Centre for Individual Rights quickly obliged. At the oral argument in January, Justice Alito and his fellow conservatives made no secret of their willingness to abandon the agency-fee model. It was all over, or so it seemed, when Anthony Kennedy, often the swing justice, told one of the unions’ supporters that the argument for fair-share fees “makes no sense”.

A win for Ms Friedrichs and her disgruntled colleagues would have upended the rules for public-sector unions in California and 22 other states, threatening their funding and, possibly, their survival. But the 4-4 vote, the justices’ second deadlock since the loss of Scalia, will preserve agency fees until the next promised lawsuit challenging them works its way to the Supreme Court. If the Senate eventually sees fit to hold confirmation hearings on Mr Scalia’s successor—something that seems unlikely to happen before the next president is elected—the fate of organised labour will fall to the 113th justice.