Washington ? Chief Justice John G. Roberts Jr. raised his right hand Monday morning and pledged to “do equal right to the poor and to the rich” in a formal ceremony attended by President Bush, Cabinet members, senators and his family and friends.

Then, less than an hour later, he got down to the business of the Supreme Court, as the justices heard arguments in a labor-management dispute involving slaughterhouse workers.

At issue is whether the workers de-serve to be paid for the time it takes them to put on required protective gear and walk to the work site.

Judges in Maine and Washington state took different sides on what federal laws require. The Supreme Court took up the cases to resolve the matter.

Roberts, attentive and businesslike, asked brief questions during the hourlong arguments to clarify points raised by the lawyers for each side. As is often the case, it was not apparent how the justices likely would rule, and the answer may not come for a few months.

The first case of the Roberts Court made for a decided contrast to the ceremony that preceded it – and the weeks leading up to the confirmation of the new chief justice.

On Thursday, just after the Senate confirmed his nomination, Roberts took an oath of office at the White House.

His formal investiture as the 109th justice of the Supreme Court came at 9:15 a.m. Monday.

With the president in attendance, the clerk of the court read a formal proclamation in which Bush appointed Roberts, with the consent of the Senate, to be the chief justice of the United States.

At age 50, Roberts is the youngest person hold that post since John Marshall, then 45, was sworn in in 1801.

As the ceremony began, Roberts sat in a chair that belonged to Marshall. After the proclamation was read, he was called to the bench while the other eight justices stood.

After Roberts swore to “administer justice without respect to persons,” the senior member of the court, 85-year-old Justice John Paul Stevens, wished him “a long and happy career in our common calling.”