But the museum, the Henie Onstad Arts Center, founded in 1968 by the Olympic skating champion Sonja Henie and her husband, the shipping magnate Niels Onstad, says Mr. Onstad bought the painting in good faith more than 60 years ago, giving the center ownership rights to the work under Norwegian law. The law requires a minimum of 10 years’ possession.
The museum, outside Oslo, said it did not know the painting had once been Nazi plunder, but it does not contest that, in light of the evidence. It says that it is continuing to negotiate with the heirs and to study the work’s provenance, and that it will discuss the family’s request at a board meeting next month.
“We need to investigate this matter properly,” said the museum’s director, Tone Hansen. “It is too early to draw any conclusions. We are in dialogue with the family and will continue to be so.”
She added, “This case has other aspects than pure legal aspects that have to be taken into consideration.”