A tie vote by the Supreme Court has preserved a rule some observers called a “life-or-death” matter for public employee unions.

The case, Friedrichs v. California Teachers Association, revolved around the “forced” union dues rule, which required some California teachers to pay fees to unions even if they weren’t members and did not want to join. Similar rules are currently in place in 25 states and the District of Columbia.

The Supreme Court’s 4-4 vote preserves those rules, to the relief of many union leaders. Many experts forecasted that the rules would be overturned; those predictions changed after the February death of Justice Antonin Scalia left a vacancy on the court.

Labor officials said overturning the 38-year legal precedent could weaken unions’ power, threaten membership and deplete union funds. The fees collected through the rule are typically put toward collective bargaining, which proponents of the rule say benefits all employees.

Opponents of the forced dues rule argue that it violates their First Amendment Rights. Terry Pell, president of the Center for Individual Rights, which brought the case on behalf of the teachers, said in a press release that the case was “too significant” to settle for a split vote. Pell said the group plans to file a petition for a re-hearing.

“A union cannot claim to represent the interest of all workers if there is ongoing doubt about the constitutionality of its forcible collection of millions of dollars in dues. Either compulsory dues are an acceptable exception to the First Amendment or they are not,” Pell said. “ A full court needs to decide this question and we expect this case will be reheard when a new justice is confirmed.”