A bill signed into law this week by California Governor Gavin Newsom may signal the beginning of the end of a decades-long dispute between the Museo Thyssen-Bornemisza in Madrid and the heirs of a Jewish collector over the rightful ownership of a work sold under duress during the Nazi regime. In 1939, Lilly Cassirer Neubauer was forced to sell an 1897 oil by Camille Pissarro to a Nazi art appraiser in order to flee Germany before the impending war. According to court documents, the Pissarro, titled Rue Saint-Honoré in the Afternoon, Effect of Rain, fetched only $360 (modern USD). The...