This month, the court agreed to hear a case on the question Justices Breyer and Souter anticipated, one that will test whether there is indeed a constitutional line Congress may not cross when it comes to the public domain.

The new case asks whether Congress acted constitutionally in 1994 by restoring copyrights in foreign works that had belonged to the public, including films by Alfred Hitchcock and Federico Fellini, books by C. S. Lewis and Virginia Woolf, symphonies by Prokofiev and Stravinsky and paintings by Picasso, including “Guernica.”

“The works that qualify for copyright restoration probably number in the millions,” Marybeth Peters, the United States register of copyrights, said in 1996.

The plaintiffs in the new case, Golan v. Holder, are orchestra conductors, teachers and film archivists who say they had relied for years on the free availability of works in the public domain that they had performed, adapted and distributed.

The 1994 law, they told the justices, “did something unprecedented in the history of American intellectual property law and constitutionally profound.”

Lawrence Golan, the lead plaintiff, teaches conducting at the University of Denver and is the music director and conductor of the Yakima Symphony Orchestra in Washington State. He said the 1994 law made it very difficult for smaller orchestras to play some seminal 20th-century works that had once been a standard part of their repertories.

“Once you own a Beethoven symphony, you own it till it falls apart,” he said. “That used to be the case with Stravinsky, Shostakovich and Prokofiev. Now an orchestra that wants to play, say, Shostakovich’s Fifth has to rent it for $800 for one performance.”