In the case of William Fiore v. Gregory White, Warden et al., 1999, the U.S Supreme Court was tasked with determining whether a state court's reinterpretation of a criminal statute could be applied retroactively to uphold a conviction. The petitioner, William Fiore, had been convicted under Pennsylvania law for operating an illegal hazardous waste facility. However, after his conviction and unsuccessful appeal in state court, the Pennsylvania Supreme Court clarified that operation without proper permits (Fiore’s offense) did not constitute violation of this law. Despite this clarification which effectively nullified his crime as per state laws at time of conduct and trial both; he remained incarcerated because lower courts refused to apply this new interpretation retrospectively on procedural grounds. The U.S Supreme Court initially certified question to Pennsylvania Supreme Court if their decision was indeed new interpretation or mere clarification - latter would mean it applies from inception hence making Fiore’s act non-criminal ab initio itself. On receiving confirmation that it was indeed just a clarification i.e., restating original legislative intent; US supreme court held that due process clause mandates retrospective application in such cases where person is being held for something which wasn’t crime when committed according to then existing laws – thus ordering release/remedy for Mr.Fiore.

In the dissenting opinion for William Fiore v. Gregory White, Warden, et al., Justice Scalia disagreed with the majority's decision to grant relief based on a state court interpretation of its own law. He argued that federal courts should not intervene in such matters and that it was inappropriate to apply a "new rule" retroactively in this case. Scalia contended that Pennsylvania’s Supreme Court did not announce a new legal standard but merely interpreted an existing one; thus, there was no violation of due process rights as claimed by Fiore. Furthermore, he expressed concern about the potential implications of this ruling for federalism and comity between state and federal courts.