The heirs of the Jewish-Hungarian banker and world renowned art collector, Baron Mór Lipót Herzog, have filed a lawsuit in United States District Court in Washington demanding the return of the art collection they say is rightfully theirs, reports Carol Vogel for the New York Times.

The collection, valued at $100 million, has been hanging in Hungarian museums, where it was left for safekeeping during World War II or placed after being stolen by the Nazis and later returned to Hungary. After years of petitions to have the works returned to the heirs and a 2008 Hungarian court’s ruling that the government was not required to return them, Tuesday’s lawsuit in Washington marks the largest legal action of its kind.

The suit includes an unprecedented twist: in addition to the more than 40 artworks identified in the filing — including paintings, sculptures and other works by masters like El Greco, Lucas Cranach the Elder, Zurbarán, van Dyck, Velázquez and Monet — lawyers are also asking the Hungarian government for an accounting of all art from the Herzog family in its possession.

Michael S. Shuster, a lawyer for the Herzog family, said that Hungary had been “one of the countries that has been the most recalcitrant” about returning looted art.

“While other countries have cooperated,” he said, “Hungary has been bucking that trend.”

David de Csepel, an heir of the Baron Mór Lipót Herzog, who is demanding the return of his great-grandfather’s collection.