In mid 00-th, famous case of Maria Altmann and the return of five Klimt' s paintings, including Golden Adele, hit the headlines. The legally most interesting detail in this case was that Maria Altmann was authorized to proceed with a civil action against Austria in a US federal district court. The very interesting speech of Mrs.Altmann' s lawyer, Los Angeles attorney E. Randol Schoenberg, describing a long way to finding US court jurisdiction over the case is on the youtube at https://www.youtube.com/watch?v=zTi0q6AVDIY (The Recovery of Nazi-Looted Art: The Bloch-Bauer Klimt Paintings).
According to Reuters, in the beginning of April 2017, another US court found its jurisdiction in the claim against the other country. A federal court in Washington accepted jurisdiction against Germany in a claim seeking the return of the Nazi-looted collection of old gem-studded busts of saints and golden crucifixes (U.S. court approves lawsuit against Germany over claims of Nazi art theft, http://www.reuters.com/article/us-usa-nazi-artwork-idUSKBN17601L )
In 1935 Jewish art dealers in Germany sold a Welfenschatz collection to the state of Prussia, then being administered by Hermann Goering. As per the lawyers of the heirs, pressure from the Nazis caused the dealers to sell the art for just 35 percent of its market value. Moreover, it is said that the money the dealers received was deposited into a bank account they were unable to access because it was blocked by the Nazis.
Defending its position in the current jurisdiction case, Germany argued the case had already been heard before a German commission assessing Nazi-era property claims, which found the low sales price being a product of an art market disruption during the Great Depression - not because the Jewish art collectors were persecuted.
Nevertheless, the judge stated that since the Nazis’ organized plunder of Jewish property was part of their later genocide of the Jews - a crime under international law - the court had jurisdiction to hear the case. (information from: http://www.reuters.com/article/us-usa-nazi-artwork-idUSKBN17601L )