Republic of Austria v. Altmann
Republic of Austria v. Altmann, 541 U.S. 677 (2004), was a case in which the Supreme Court of the United States held that the Foreign Sovereign Immunities Act, or FSIA, applies retroactively to acts prior to its enactment in 1976.
Source: Wikipedia — Republic of Austria v. Altmann (CC BY-SA 4.0)