MADISONCENTER FOR AMERICAN LEADERSHIP
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The Constitution,
connected.

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Discover the ideas that hold a republic together.

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The constitutional text

Article I · Section 9

Select any highlighted phrase to understand what it means.

The Migration or Importation of such Persons as any of the States now existing shall think proper to admit, shall not be prohibited by the Congress prior to the Year one thousand eight hundred and eight, but a Tax or duty may be imposed on such Importation, not exceeding ten dollars for each Person

The Privilege of the Writ of Habeas Corpus shall not be suspended, unless when in Cases of Rebellion or Invasion the public Safety may require it.

No Bill of Attainder or ex post facto Law shall be passed.

[No Capitation, or other direct, Tax shall be laid, unless in Proportion to the Census or Enumeration herein before directed to be taken.]*

No Tax or Duty shall be laid on Articles exported from any State

No Preference shall be given by any Regulation of Commerce or Revenue to the Ports of one State over those of another: nor shall Vessels bound to, or from, one State, be obliged to enter, clear, or pay Duties in another.

No Money shall be drawn from the Treasury, but in Consequence of Appropriations made by Law; and a regular Statement and Account of the Receipts and Expenditures of all public Money shall be published from time to time.

No Title of Nobility shall be granted by the United States: And no Person holding any Office of Profit or Trust under them, shall, without the Consent of the Congress, accept of any present, Emolument, Office, or Title, of any kind whatever, from any King, Prince, or foreign State.

Source: National Constitution Center edition. Original wording is preserved; commentary explains historical and superseded provisions.

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Article I, Section 9, Clause 3b

No retroactive criminal disadvantage

Current text
or ex post facto Law shall be passed. [

What it means

The Ex Post Facto Clause forbids retroactive penal legislation of the prohibited kind, such as criminalizing past conduct or increasing its punishment after the fact. It protects people against a government changing the criminal rules backward in time.

Historical setting

Federalist 44 treated retrospective penal laws as contrary to basic principles of just government. The Constitution separately applies the prohibition to federal and state lawmaking.

What it does

The principle supports fair notice and constrains legislative retaliation after conduct has occurred. It is not a general statement that every law affecting past events, including all civil regulation, is unconstitutional.

Debate & interpretation

Difficult applications ask whether a nominally civil measure is actually punitive or whether a procedural change creates the forbidden disadvantage. The label chosen by lawmakers cannot alone decide the constitutional question.

A common misreading

Ex post facto does not mean every retrospective law; the constitutional prohibition has a specifically penal focus.

Think it through

Why is increasing a penalty after the act different from announcing a stricter penalty for future conduct?

Follow the connection

Sources & further reading

Original Madison Center commentary. Explanations distinguish the text, historical context, and interpretive disagreements.

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