The Supreme Court’s justices returned to work Monday in their grand courtroom for the first time in 19 months, but little seemed the same as when the coronavirus pandemic forced their departure.

In a first for an oral argument at the court, Justice Brett M. Kavanaugh participated by telephone from home after testing positive for the coronavirus last week. The courtroom was largely empty, with about two dozen reporters scattered around the seating gallery, along with the justices’ clerks. All spectators, including the arguing attorneys, wore N95 masks.

And most significantly, Justice Ruth Bader Ginsburg, who died a little more than a year ago, has been replaced by Justice Amy Coney Barrett, who was seated beside her colleagues on the mahogany bench for the first time since she joined the court in October 2020.

She has been taking part in the court’s arguments, like the rest of the justices, via teleconference. Her husband, Jesse Barrett, was one of three spouses to attend Monday’s proceeding, as did retired justice Anthony M. Kennedy.

The justices, including Kavanaugh, all have been vaccinated, according to the court, and they are regularly tested. At Monday’s hearing, all were unmasked except for Justice Sonia Sotomayor, who was diagnosed with diabetes as a child and wore a black face covering to match her robe.

The court remains closed to the public and open only for official business. Reporters covering the proceedings and the lawyers arguing before the court were not required to be vaccinated, but had to receive a negative result on a recent coronavirus test. Lawyers who get a positive reading will be required to make their arguments via telephone.

The court has a controversial term ahead, hearing disputes on gun control, religious rights and what could be a monumental ruling on abortion rights. Mississippi is asking the court to overturn the constitutional guarantee to abortion the Supreme Court established in Roe v. Wade in 1973.

But the cases heard Monday were decidedly less controversial. And the only sign of the drama to come was a rally held by those opposed to abortion on the sidewalk in front of the court.

The first case Monday was a long-running dispute in which Mississippi is suing the city of Memphis and the state of Tennessee for $600 million over a claim Memphis is harming its neighbors to the south by drawing water from the Middle Claiborne Aquifer. It lies below the two states, as well as others.

From the tone of the hearing, Mississippi seemed likely to lose, and the questioning was orderly and at times even lighthearted.

In asking about a state’s authority over natural resources within its borders, Chief Justice John G. Roberts Jr. wondered about capturing wild herds of burros that might wander from one state to another. Justice Stephen G. Breyer pondered if there would be a case should someone find a way to capture and transport San Francisco’s famous fog.

The point, as Justice Neil M. Gorsuch indicated, was that the court had not weighed in before on underground water that flows between states, and justices needed to figure out the outer limits of the kinds of claims the court should hear.

In the other case, the justices considered a part of the Armed Career Criminal Act, which provides longer mandatory sentences for a repeat offender. The question was whether William Wooden’s conviction for breaking into 10 units at a storage facility on the same day should count as one offense or 10.

The justices appeared favorable to Wooden’s argument it should be seen only as one.

As a concession to safety, the arguing lawyers have been moved farther away from the justices. And the justices have imposed new order to their questioning.

Justice Clarence Thomas, who went years without asking a question when the court’s rather rough-and-tumble questioning process was in place, was an active questioner Monday, as he had been when the justices asked questions in turn during the teleconference format it used last term.

The other justices seemed to wait until Thomas, the court’s longest-serving justice, had asked a question before jumping in. And the court has added a period after each advocate finishes in which justices take turns asking additional questions, in order of seniority.

Before arguments started, the justices affirmed a court decision that said residents of D.C. can’t make a claim to a vote in the House of Representatives.

A three-judge panel in Washington unanimously held that because the Constitution limits representation in the House to “the people of the several states,” the court could not grant the relief the registered voters in the nation’s capital were seeking.

The court’s brief order affirmed the decision without scheduling it for additional briefing and argument.

The court also turned down a petition from Oracle Corp. challenging a now-withdrawn Pentagon cloud-computing contract.

The Defense Department decided this summer to divide the $10 billion contract among other bidders.