Also known as: post factum · postfactum · post facto
Written by attorneys · grounded in primary & secondary sources — see below
A subsequent act or change that attaches new legal consequences to prior conduct.
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Patrick Phan completed a series of import transactions in State A before any new fee statute existed. State A then enacted a law imposing duties on those prior imports. The post-factum statute triggered a constitutional challenge under Article I Section 10.
Paul Peterson completed conduct that became time-barred under the original statute of limitations. Years later a new statute revived the expired prosecution. The post-factum revival altered the legal consequences attached to Peterson's earlier acts.
Patricia Patel engaged in conduct that was lawful when performed. Congress later passed a statute criminalizing that same conduct and applied it to her. The post-factum criminalization raised an Article I Section 9 challenge.
Paige Porter completed a transaction that later became the subject of litigation. A court considered whether post-factum changes in circumstances justified equitable relief. The analysis turned on whether the after-act altered the parties' original positions.
Piper Patel initiated a proceeding and later faced a new procedural requirement imposed by statute. The post-factum barrier affected her ability to maintain the action. The court examined whether the after-act imposed an unconstitutional condition.
Phuong Pham filed suit challenging government action. Subsequent developments occurred after the complaint was filed. The post-factum events required the court to reassess whether standing existed at the time of filing.
It refers to an after-act or an act done afterwards. In the context of the Ex Post Facto Clauses, the term identifies legislation that attaches new legal consequences to conduct completed before the law's enactment.
A statute that retroactively increases punishment or criminalizes previously lawful conduct after the conduct has occurred is an ex post facto law. The Ex Post Facto Clauses in Article I Sections 9 and 10 prohibit such after-the-fact legislative changes.
No. Only those post-factum changes that retroactively alter criminal liability or punishment violate the clauses. Civil regulatory measures or procedural adjustments that do not increase punishment are generally permissible.
…a measure was "necessary and proper" to the discharge of its substantive legislative authority, pass a bill of attainder or ex post facto law contrary to the prohibitions contained in § 9 of Art. I. No more may it vest in itself, or in its officers, the authority to appoint officers of the United States when the Appointments…