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Ex Post Facto laws

Article 24 (1780)

Laws made to punish for actions done before the existence of such laws, and which have not been declared crimes by preceding laws, are unjust, oppressive, and inconsistent with the fundamental principles of a free government.

Precedents, Following Law, and Quotations

The federal equivalent of the prohibition on passing ex post facto law can be found in the United States Constitution in Article 1.   Section 9, clause 3, prohibits the United States Congress from passing ex post facto laws.  Section 10, clause 1, prohibits the states from passing ex post facto laws.


Alexander Hamilton, Federalist Paper No. 84, “Certain General and Miscellaneous Objections to the Constitution Considered and Answered”, From McLean’s Edition, New York, (1788) , 4th paragraph:.

“The creation of crimes after the commission of the fact, or, in other words, the subjecting of men to punishment for things which, when they were done, were breaches of no law, and the practice of arbitrary imprisonments, have been, in all ages, the favorite and most formidable instruments of tyranny.”


Reference is made in Massachusetts cases to “the classical exposition of an ex post facto law [within] the primordial case of Calder v. Bull” :

“1st. Every law that makes an action done before the passing of the law, and which   was innocent when done, criminal; and punishes such action.

2d. Every law that aggravates a crime, makes it greater than it was, when committed.

3d. Every law that changes the punishment, and inflicts a greater punishment, than the law annexed to the crime, when committed.

4th. Every law that alters the legal rules of evidence, and receives less, or different, testimony, than the law required at the time of the commission of the offence, in order to convict the offender.


“Our cases have treated the ex post facto provisions within the State and Federal Constitutions in identical fashion.”

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