For more than a decade the University of Oklahoma has exhibited a piece of Nazi-looted artwork bequeathed to it by the wife of an oil tycoon.
Now, renewed claims by a family that owned the oil painting before the second world war have drawn the United States school into a fight it thought was settled in Switzerland more than 60 years ago.
Camille Pissarro's Shepherdess Bringing in Sheep, an 1886 painting that once belonged to a French Jew, fell into Nazi hands as Germany overran Europe. The school maintains it is the painting's rightful owner, citing a Swiss court decision from 1953.
However, Leone Meyer, a Holocaust survivor, has sued university president David Boren and the university in US federal court, seeking the painting's return.
Swiss records show Meyer's father was a former owner of the painting, but a judge denied a previous claim to the work because her family could not prove post-war owners obtained it in bad faith.
"I find all of this very difficult," Meyer wrote in an open letter, translated from French. "But I simply cannot surrender and say: 'oh well...' That is out of the question."
After the Swiss court rejected Raoul Meyer's claim, the Meyer family then turned down an offer to buy it back.
Oil tycoon Aaron Weitzenhoffer and his wife, Clara, bought the painting from a New York gallery in 1956. When she died in 2000, it was one of more than 30 works worth US$50 million that she donated to the university.