Ellingburg v. United States · ¶58

laws that impose coercive penalties for public wrongs. Contrary to the modern framework, it does not matter what the legislature labels the law, where it places the law, which agency it vests enforcement with, what its stated goals were, whether it provides safeguards for the accused, whether it requires a showing of scienter, or whether the conduct to which it applies is already a crime. Contra, Smith, 538 U. S., at 96; Martinez-Mendoza, 372 U. S., at 168–169. What matters is what the law does. If it punishes a public wrong—or an injury to the sovereign in its sovereign capacity—then it is subject to the Ex Post Facto Clauses. If it changes merely private relations, such as the rules of contract or property or probate, then it is not.

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