During the Weimar Republic, a consortium of German Jewish art dealers purchased a collection of medieval relics known as the Welfenschatz for preservation. When the Nazis took over Germany, they forced the consortium to sell the relics to the government for a third of their value. Heirs of the consortium failed to recover the artifacts in Germany, so they filed suit in the U.S. Germany argued that it was immune from suit under the Foreign Sovereign Immunities Act because the relics were not “property taken in violation of international law,” because the relics were taken from German citizens, which is lawful under international law under the “domestic takings rule.” The heirs argued that the purchase was an act of genocide, and thus a violation of international human rights law entitled to the Act’s exception. The district court and the D.C. Circuit both held that the lawsuit could proceed.
The Court, in a unanimous opinion by Chief Justice Roberts, reversed, holding that the Act’s exception did not apply to situations where a government took property from its own citizens, which is a purely domestic affair. The Court reasoned that the “domestic takings rule” was not set aside by the advent of international human rights laws. The Chief Justice noted, “As a Nation, we would be surprised—and might even initiate reciprocal action—if a court in Germany adjudicated claims by Americans that they were entitled to hundreds of millions of dollars because of human rights violations committed by the United States Government years ago.” Thus, American courts had no jurisdiction over the heirs’ claims.
The opinion in Federal Republic of Germany v. Philipp is here: https://www.supremecourt.gov/opinions/20pdf/19-351_o7jp.pdf