On Monday, March 2, 2026 StandWithUs, along with the Monuments Men and Women Foundation, Jamie Kastner, Laura Baron Kastner, and the Dr. David Milch Foundation, filed an amicus curiae brief with the U.S. District Court for the Central District of California in a lawsuit seeking to return artwork taken by the Nazis during the Holocaust that is currently housed in a Spanish national museum – The Thyssen-Bornemisza Collection.
The painting, “Rue Saint-Honoré in the Afternoon. Effect of Rain,” is a Paris streetscape by impressionist master Camille Pissarro. The Nazis forced its Jewish owner, Lilly Cassirer, to sell the painting for a mere fraction of its value in 1939. Upon discovering the painting in the Thyssen-Bornemisza Museum, in 2005 the Cassirer family filed a lawsuit in the United States to recover the painting from the Spanish government.
The main legal issue in this case is whether California or Spanish substantive law governs the dispute. Spanish law would give ownership to the museum and California law would give ownership to the family.
In January 2024, the U.S. Court of Appeals for the Ninth Circuit ruled that Spanish substantive law applies. But later that year, California enacted a new law that requires courts to apply California substantive law to cases like these. In March 2025, the U.S. Supreme Court vacated the Ninth Circuit’s decision and remanded the case in light of California’s new law.
Despite the new California law, the museum argues that California substantive law is inconsistent with United States federal law and policy and should not be applied. The amicus brief explains the why the museum’s position is incorrect by showing that the history of federal law and policy favors the return of stolen Nazi artwork to their rightful owners. The brief first discusses the Nazis’ campaign of art theft and the response to it in the immediate aftermath of WWII. The brief next shows that the policy of the United States and its laws favor the return of art stolen by the Nazis. The brief concludes by explaining why California’s new law aligns with “federal laws, policies, and international agreements[.]”
StandWithUs is hopeful the District Court will rule in the family’s favor and this precious piece of art will finally be returned to its rightful owners.
