The family of a deceased American modern artist is suing the Philadelphia Museum of Art for ownership of a work of art by Dutch painter Piet Mondrian, which the plaintiffs say was seized by the Nazis in the 1930s.

The plaintiffs brought the action under the Holocaust Expropriated Art Recovery Act of 2016, but the defendants contend that the suit belongs in federal court because it raises questions of whether that act protects work that Nazis took outside the scope of their genocidal policies.