Written by Bard Wilkinson, CNN

Britain's National Gallery is to face an appeal in the United States Supreme Court after being sued for the return of a "stolen" Matisse portrait by descendents of the painting's subject.

Three grandchildren of Greta Moll have demanded that the museum pay $30 million compensation or return "Portrait of Greta Moll," which the French artist painted in 1908.

The family alleges that the painting was stolen from them in 1947 during the upheaval following the Soviet invasion of Berlin after the end of World War II.

The London museum, which has owned the portrait since 1979, has defended its position saying that, because it disappeared during Soviet rather than Nazi occupation, it was not bound to return it.

"Neither of the two US courts, which have already heard argument on this point, gave it any credibility," the museum said in a statement. "If the Supreme Court declines to consider this point no further avenue of appeal will be open to the claimants."

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"This is not a case involving Nazi looted art; the claimants allege that the family lost the painting due to the dishonest act of a family friend in 1947, many years before it was purchased in good faith by the National Gallery," it added.

The museum declined to comment further.

The grandchildren are British-born Oliver Williams and Margarete Green, and Iris Filmer of Germany. They have been trying to gain possession of the painting for eight years.

According to them, Moll's husband, Oskar, bought the painting from Matisse, but during the war gave it to a student in Switzerland for safekeeping. According to the family's previous accounts of the portrait's fate, the student absconded with it. The painting passed through several US art galleries until it was bought by the National Gallery in 1979, two years after Moll's death.

The grandchildren's US lawyer, David Rowland, issued a statement saying: "At the heart of the issue here is the question of whether cultural property, lost, stolen or looted due to war, should be returned to its true owners."











































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"Most right thinking institutions and persons recognize that war and its aftermath strains civil society to its limits, but when order is restored after war, cultural property that was uprooted due to it, should be restored to its rightful ownership. Sadly, that has not been the case here."

According to previous reports , the family sued after the Spoliation Advisory Panel, a British government body reviewing Holocaust-era claims, said it lacked jurisdiction because the Nazi era ended in 1945, two years before the alleged theft.

The grandchildren sued in New York because they say the National Gallery has commercial interests in the US.

New York circuit court and a federal appeal court have ruled that sovereign immunity shielded the museum and Britain from having to return the painting.

The National Gallery released a statement last year saying that several years after the war ended, and following the death of her husband in 1947, Moll left Germany for Wales.

"At no point was it ever suggested to us that the painting had been stolen from the family, or that the family had any concerns with the painting being on display here at the National Gallery. We only became aware of these when we received a letter from US lawyers acting for them in 2011," the statement said.

Moll sat for the painting, which experts consider a masterpiece of Matisse's "fauve" period, for 30 hours. According to the National Gallery's website , Moll, who was herself a sculptor and painter, and her husband were pupils of Matisse.

"After seeing a painting by Veronese in the Louvre in Paris, Matisse reworked the portrait extensively, broadening the arms and emphasizing the curve of the eyebrows, to give the figure grandeur and monumentality," the post says.

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The case is one of many seeking to recover art stolen or misappropriated in connection with World War II.

Artworks looted by the Nazis have been returned to galleries and to the heirs of their original owners in various countries around the world.

In September, a Renoir painting stolen by the Nazis was returned to its rightful owner in the US.

Experts believe many of the discovered paintings, drawings and sculptures -- including works by Monet, Picasso and Rodin -- were looted by the Nazis from Jewish collectors or dealers.