The US Supreme Court Thursday ruled in favor of Holocaust survivor heirs who sought to repossess a Pissarro painting that was stolen by Nazis during World War II.

In Cassirer v. Thyssen-Bornemisza Collection Foundation, the Cassirer family sought to repossess a Camille Pissarro painting that was stolen by Nazis in 1939. The Thyssen-Bornemisza Collection Foundation, an entity created by Spain, purchased the painting in the 1990s.

The Cassirer family sued the foundation in a California federal court after learning that the painting was listed in the foundation’s museum catalog. The lawsuit invoked the Foreign Sovereign Immunities Act of 1976 (FSIA) because the foundation is an “instrumentality” of Spain. The district court ruled in favor of the foundation, and the US Court of Appeals for the Ninth Circuit affirmed.

The Supreme Court then agreed to hear the case to decide whether a court in an FSIA case should apply the forum state’s choice-of-law rule or use a federal choice-of-law rule. The choice-of-law rule that applies would likely determine whether the museum or the Cassirers will retain the painting. The court heard oral arguments in the case in January.

On Thursday, the Supreme Court held that a court should apply “whatever choice-of-law rule the court would use if the defendant were not a foreign-state actor, but instead a private party.” In this case, that meant applying California’s choice-of-law rule.

The court reasoned that the FSIA was never “intended to affect the substantive law determining the liability of a foreign state or instrumentality” in a lawsuit. When foreign states do not have immunity from a lawsuit, they are subject to the same liability rules as private parties. That means that “the standard choice-of-law rule must apply.”

Because of this, the court vacated the Ninth Circuit’s judgment and remanded the case for further proceedings.

The Supreme Court also issued judgments in several other cases on Thursday, including US v. Vaello Madero, City of Austin v. Reagan National Advertising of Austin, Boechler v. Commissioner of Internal Revenue, and Brown v. Davenport.