Employers who stiff their workers or discriminate against them just got a big lift from the Supreme Court, which issued a major ruling Monday making it easier for companies to avoid employee lawsuits.

The 5-4 ruling upheld employers’ use of class-action waivers in arbitration agreements. By signing these controversial provisions, workers give up their right to band together and sue in court for back pay or damages, and are instead forced to take their disputes to arbitrators individually.

Arbitration agreements have become a common way for employers to stifle lawsuits that could lead to large plaintiff classes and big payouts. Workers backed by employee groups and labor unions challenged their employers’ use of these agreements, claiming they ran afoul of the National Labor Relations Act, or NLRA, which guarantees workers the right to join forces in “mutual aid and protection.”

The employer-friendly conservative majority on the court decided against the workers. They ruled that collective bargaining law does not supersede federal law that established the arbitration process, therefore making the class-action waivers in employment contracts legitimate.

Justice Neil Gorsuch wrote the opinion for the conservative majority, saying Congress did not write the NLRA to “displace” federal arbitration law.

“The policy may be debatable but the law is clear: Congress has instructed that arbitration agreements like those before us must be…