Any transaction in 1935 where the sellers on the one side were Jews and the buyer on the other side was the Nazi state itself is by definition a void transaction, Mr O'Donnell said.
The organisation that oversees Berlin's museums, the Prussian Cultural Herit- age Foundation, says that the collectors were not forced to sell the pieces, arguing among other things that the collection was not even in Germany at the time of its sale.
Last year a German government com- mission created to help resolve restitution claims evaluated both arguments and rec- ommended that the collection stay in Ger- many. The commission wrote that after thoroughly investigating the sale process, it came to the conclusion that it was not a "forced sale due to persecution'.