(JTA) — An Oklahoma lawmaker is calling for an investigation into the University of Oklahoma art museum over a Nazi-looted painting.

State Rep. Mike Reynolds in a letter to the president of the American Alliance of Museums, a national museum accreditation bureau, called for the probe into the accreditation status of the Fred Jones Jr. Museum of Art, the Oklahoman daily reported.

Reynolds’ request comes in the wake of a 2013 lawsuit against O.U. and the recent resignation of the museum’s director, Emily Neff.

The lawsuit was filed by Leone Meyer, a Parisian who sued to recover the painting “Shepherdess Bringing In Sheep.” Meyer alleged that the 1866 artwork was stolen from her father, a Jewish businessman in Paris, during the Nazi occupation of France.

O.U. officials have refused to return the work; they don’t dispute that it was looted by the Nazis.

The painting was among 30 works totaling $50 million donated to the university in 2000 by the estate of Clara Weitzenhoffer, the late wife of Oklahoma oilman Aaron Weitzenhoffer.

“The university does not want to keep any items which it does not legitimately own,” the university’s president, David Boren, told the Oklahoman. “However, the challenge to the university, as the current custodian of the painting, is to avoid setting a bad precedent that the university will automatically give away other people’s gifts to us to anyone who claims them.”

In his letter Reynolds, who has been a vocal critic of the university for not returning the painting, said the university violated the American Alliance of Museum’s accreditation standards when it failed to research the origins of the paintings.

The letter, which is detailed in the Oklahoman, also said that Neff resigned the day after the Oklahoma House Government Modernization and Accountability Committee sent her a notice raising concerns about the museum’s handling of the case.