Also known as: ex post facto clauses · ex post facto · ex post facto law · ex post facto laws
Written by attorneys · grounded in primary & secondary sources — see below
A constitutional prohibition that bars Congress and the states from enacting criminal laws retroactively criminalizing conduct lawful when performed, increasing punishment for past acts, or altering rules of evidence to the defendant's disadvantage.
Emmett Egan raised rents on his apartment buildings four years earlier under then-lawful lease terms. After Franklin enacted a statute making such increases a felony and authorizing prosecution from old records, the district attorney charged Egan. The court dismissed the charges because the statute retroactively criminalized past lawful conduct.
Elijah Edwards committed a sex offense more than a decade earlier when the statute of limitations had already expired. California later passed a law reviving such prosecutions, and prosecutors filed charges against Edwards. The Supreme Court held the revival statute violated the Ex Post Facto Clause by reopening punishment for completed conduct.
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Esther Eisenberg, a museum curator, acquired cultural artifacts fifty years ago in full compliance with then-existing export rules. Congress later enacted a statute making such acquisitions a federal crime and indicted Eisenberg solely on the basis of those prior transactions. The court dismissed the indictment because the statute retroactively criminalized lawful past conduct.
Evelyn Ellison sold counterfeit goods last year when the maximum prison term was five years. After Congress raised the mandatory minimum and applied the new penalties to all prior offenses, the sentencing judge imposed a longer term on Ellison. The court vacated the sentence because the retroactive increase in punishment violated the Ex Post Facto Clause.
Eric Espinoza published a novel decades earlier under a copyright term that had already expired. Congress later lengthened copyright terms and applied the extension to works whose protection had lapsed. The court upheld the extension because it did not impose criminal punishment or alter criminal liability for past acts.
Emily Ellis distributed materials that were lawful under the prevailing obscenity test when she acted. After the Supreme Court announced a new standard, prosecutors sought to apply it retroactively to her earlier distribution. The court rejected the application because the new standard could not increase criminal liability for completed conduct.
The clause prohibits legislatures from making conduct criminal that was lawful when performed, increasing punishment for past acts, or changing evidentiary rules to make conviction easier.
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The clause applies only to criminal punishment. Civil remedial measures such as treble damages for consumer compensation do not violate it even when imposed retroactively, unless the measure functions as punishment.
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No. Extending a statute of limitations after it has expired and applying the extension to already-barred offenses violates the clause because it reopens the possibility of punishment for past conduct.
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Purely procedural changes that do not increase the quantum of punishment may be applied retroactively. Changes that raise the penalty attached to completed conduct are forbidden.
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…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…