Manhattan art dealer Hillel "Helly" Nahmad, who is serving prison time for his role in running an illegal gambling ring, has been sued by a Frenchman for allegedly not disclosing the location and owner of a $20 million Amedeo Modigliani painting looted by the Nazis.

Nahmad and his billionaire father David Nahmad were sued in Manhataan Supreme Court by Phillippe Maestracci, whose Jewish grandfather Oscar Stettiner was an art dealer in Paris until the Nazis invaded in 1939.

Maestracci claims that the Nahmads hid behind a corporation called International Art Center to avoid a federal lawsuit over Modigliani’s “Seated Man with a Cane.”

He wants disclosure on who owns the 1918 painting, who runs IAC, and where the work is located. 

Richard Golub, an attorney for the gallery, stated, “This painting was bought at a Christie’s London auction in 1996 by IAC, and the location of the painting is a matter of public record.” A previous federal lawsuit brought by Maestracci against the Nahmads was withdrawn, Golub noted.