SAN FRANCISCO — In the first art law case of his 50-plus year legal career, David Boies has helped convince an appellate court to revive a long-running lawsuit over a Nazi-looted painting by French impressionist Camille Pissarro.

A three-judge panel of the U.S. Court of Appeals for the Ninth Circuit on Monday reversed a decision tossing claims that Boies’ clients are the rightful owners of “Rue Saint-Honoré, après-midi, effet de pluie,” a masterpiece that has been appraised at more than $30 million. Lilly Cassirer Neubauer, the great-grandmother of the plaintiffs, lost the painting in 1939, accepting the modern day equivalent of $360 for it after an art dealer appointed by the Nazi government seized it to conduct an appraisal.