The United States Supreme Court granted certiorari and heard oral arguments in the case in January 2016, releasing their opinion in April 2016. A 6–2 majority found that § 8772 was not unconstitutional, because it "changed the law by establishing new substantive standards" —essentially, that if Iran owns the assets, they would be available for execution against judgments against Iran—for the district court to apply to the case. Justice Ruth Bader Ginsburg, writing for the majority, explained that the federal judiciary has long upheld laws that affect one or a very small number of subjects as a valid exercise of Congress' legislative power and that the Supreme Court had previously upheld a statute that applied to cases identified by docket number in Robertson v. Seattle Audubon Society (1992). The majority also upheld § 8772 as a valid exercise of Congress' authority over foreign affairs. Prior to the enactment of the Foreign Sovereign Immunities Act (FSIA) in 1976, Congress and the Executive branch had authority to determine the immunity of foreign states from lawsuits. Despite transferring the authority to determine immunity to the courts through the FSIA, the majority contended that "it remains Congress' prerogative to alter a foreign state's immunity."
Chief Justice John Roberts, joined by Justice Sonia Sotomayor, dissented and harshly criticized the majority's holding. After providing historical context for the separation of powers between the legislature and judiciary found in Article III of the United States Constitution, the Chief Justice explained that § 8772 is a type of unconstitutional breach of the separation "whereby Congress assumes the role of judge and decides a particular case in the first instance." In his view, § 8772 is no different than a hypothetical law applying to a case Smith v. Jones in which the legislature says simply "Smith wins". In the Chief Justice's view, § 8772 was not a valid exercise of Congress' foreign affairs authority, contending that Congress and the Executive branch have sufficient authority that they do not need to "seize" the judiciary's power to "make a political decision look like a judicial one." Quoting James Madison in Federalist No. 48, the Chief Justice lamented that this case "will indeed become a blueprint for extensive expansion of the legislative power at the judiciary's expense, feeding Congress's tendency to 'extend the sphere of its activity and draw all power into its impetuous vortex.'"
The decision came as