The Courthouse News Service has this suit against the Helly Nahmad gallery:
Philippe Maestracci sued the Helly Nahmad Gallery, seeking return of the 1918 Modigliani painting, “Seated Man With a Cane.” Maestracci says he is sole heir of Oscar Stettiner, a Jewish art dealer who owned a Paris art gallery, and the Modigliani painting. […] In 1939 Stettiner was forced to flee Paris “with the threat of Nazi invasion looming,” leaving his art collection behind. […] Stettiner died in 1948. Since then his heirs “have made reasonable and diligent efforts” to find his art collection, Maestracci says. He says he located it in 2008, when Sotheby’s published it as being consigned for sale by the Helly Nahmad Gallery.
Man Demands Nazi-Looted Modigliani (Courthouse News Service)