This article was updated at 9:30 a.m. to correct Chief Justice John Roberts’ title.

PORTLAND — The chief justice of the United States made an exception Monday to his family’s rule that they do nothing in August but spend time on Hupper Island, off the coast of St. George.

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John Roberts AP

Chief Justice John Roberts Jr. left his summer home in the midcoast to mark the 200th anniversary of the Nathan and Henry Cleaves Law Library with Maine’s legal community.

Roberts addressed 300 people, including Gov. Paul LePage, during a lunchtime celebration of one of the nation’s oldest law libraries. His remarks, like those of U.S. District Judge D. Brock Hornby and Chief Justice Leigh Saufley of the Maine Supreme Judicial Court, mixed erudition and good-natured humor, sometimes of the self-deprecating sort.

“When judges or justices speak in court, there’s a good chance we will disappoint half of the people who appear before us. When we speak in public, we have a good chance of disappointing everyone,” Roberts said. “Despite that clear and present danger, I was happy to accept your kind invitation to visit this afternoon.”

Roberts said he was glad because the invitation was endorsed by people he respects and it gave him an opportunity to visit with the state and federal judges of Maine. And, he said, the occasion afforded him some vindication for all the times librarians have told him to be quiet.

The roots of Cleaves stretch back to 1811 — nine years before Maine granted Massachusetts its freedom, as Saufley described it. At the time, subscribers, members of the Cumberland County Bar, agreed to support the Cumberland Law Library.

Over the years, the library went through name and organizational changes, survived fires in 1866 and 1908, and operated in various places before it evolved into its current form — a nonprofit organization in the Cumberland County Courthouse.

Henry B. Cleaves was a governor of Maine, as well as a Portland city solicitor, state attorney general and Civil War lieutenant.

Cleaves, who died in 1912, bequeathed his law library to the county bar association with the stipulation that it be in his name and that of his late older brother, Nathan, who was also a lawyer.

It officially opened in the federal courthouse in 1930 and received permission to move to the county courthouse 10 years later.

A branch library remained in the federal courthouse until 1955.

Hornby said the library has been a remarkable resource during his career, from the time he was a lawyer to when he was a justice on Maine’s supreme court to his current post on the federal bench.

“Without Cleaves and its librarians, I — and I think many of you — would look a lot dumber,” he said.

Roberts said that while he appreciates the efficiency of the information age, he worries that modern methods of legal research could make it easier to confuse the collection of information with the acquisition of knowledge.

“I hope that the generations that follow will get a chance to experience learning in the enriching environment of a real library and not just a virtual one — a library where you feel connected to knowledge in a very tangible way and also connected to those working alongside you in a similar pursuit for knowledge,” he said, “even if they’re representing an adversary or even if they’re working for a judge who will decide your case.”