Chief Justice John G. Roberts Jr. and Justices Anthony M. Kennedy, Clarence Thomas and Samuel A. Alito Jr. joined the majority opinion.

The cases featured an unusual element: Lawyers for the federal government appeared on both sides.

The Obama administration had filed a brief supporting the workers on behalf of the National Labor Relations Board. The Trump administration reversed course, and it argued on behalf of the employers. The labor board’s general counsel, however, argued for the workers.

The three consolidated cases decided Monday concerned charges that employers had underpaid their workers. The workers’ employment contracts required that they resolve such disputes in arbitration rather than court and, importantly, that they file their claims one by one.

Arbitration clauses in employment contracts are a recent innovation, but they have become quite common. In 1992, Justice Ginsburg wrote, only 2 percent of non-unionized employers used mandatory arbitration agreements, while 54 percent do so today. Some 23 percent of employees not represented by unions, she wrote, are subject to employment contracts that require class-action waivers.

Under those contracts, Justice Ginsburg wrote, it is often not worth it and potentially dangerous to pursue small claims individually. “By joining hands in litigation, workers can spread the costs of litigation and reduce the risk of employer retaliation,” she wrote.

The contracts may also encourage misconduct, Justice Ginsburg wrote.

“Employers, aware that employees will be disinclined to pursue small-value claims when confined to proceeding one-by-one, will no doubt perceive that the cost-benefit balance of underpaying workers tips heavily in favor of skirting legal obligations,” she wrote, adding that billions of dollars in underpaid wages are at issue.

Justice Ginsburg added that requiring individual arbitrations can produce inconsistent results in similar cases, particularly because arbitrations are often confidential.

