WASHINGTON (AP) — The Supreme Court opened a high-profile term Monday with a case about employees’ rights that could affect an estimated 25 million workers.

Justice Neil Gorsuch, in his first full term on the bench, was silent during an otherwise lively argument in which the justices seemed closely divided.

The case is of considerable importance to employers and their workers because it involves how employees can complain about pay and conditions in the workplace.

The issue is whether businesses can force employees to individually use arbitration to resolve disputes. The case pits labor laws intended to allow workers to band together against an older law encouraging the use of arbitration, instead of the courts.

Justice Ruth Bader Ginsburg, seeming to speak for the court’s liberal wing, said the importance of collective action is “there is strength in numbers. You have to protect the individual worker in a situation where he can’t protect himself.”

The conservative justices appeared to have a different view of the case.

Chief Justice John Roberts sounded concerned about a ruling for the workers, which he said “would invalidate contracts for 25 million employees.” That’s the estimated number of non-union workers who have contracts with the individual arbitration provision that is at the heart of the case.

One of the term’s biggest cases, about partisan advantage in drawing electoral districts, is set for argument Tuesday. It has the potential to reshape American politics, if the court for the first time rules that political maps can be excessively partisan.

The justices took their seats just after 10 o’clock on the first Monday in October, the day prescribed in federal law as the start of the high court term. Roberts quickly declared the last term over and the new one, begun. Then he welcomed the nation’s new solicitor general, Noel Francisco, who was confirmed by the Senate last month as the Trump administration’s top Supreme Court lawyer.

Francisco’s appearance was one of several signs of changes at or involving the court since Donald Trump’s election as president.

Trump appointed Gorsuch to fill the seat that had been vacant since Justice Antonin Scalia’s death. President Barack Obama had nominated Judge Merrick Garland for the vacancy, but Senate Republicans refused to act on Garland’s nomination.

Another marker of change was in the administration’s position in the employer-employee dispute. The Obama administration had sided with the workers, but Trump’s Justice Department reversed that position.

The result was the rare appearance of two lawyers for governmental agencies on opposite sides of the same case. While the Justice Department contended the businesses should win, the National Labor Relations Board argued that the workers should be protected.

A decision is expected by the spring.