Article I, Section 9, Clause 3:

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

The Supreme Court has generally rejected ex post facto challenges to laws imposing retroactive tax liability.1 In Kentucky Union Co. v. Kentucky, the Court emphasized that not all retroactive laws are ex post facto, as the prohibition on ex post facto laws applies only to retroactive criminal laws.2 The majority further opined: “Laws of a retroactive nature, imposing taxes or providing remedies for their assessment and collection, and not impairing vested rights, are not forbidden by the Federal Constitution.” 3

The Court has made clear, however, that the question of whether a law is a non-penal tax, and thus outside the scope of the Ex Post Facto Clauses, depends on how the statute functions rather than its formal classification by the legislature. In Burgess v. Salmon, the Court held that the retroactive application of a tax law that was enforceable through a fine and imprisonment was invalid on ex post facto grounds.4 The Court cautioned that “the ex post facto effect of a law cannot be evaded by giving a civil form to that which is essentially criminal.” 5

Footnotes

1

See, e.g., Carpenter v. Pennsylvania, 58 U.S. 456, 463 (1855) (law retroactively imposing a tax on certain devises in a will was not ex post facto); Bankers Trust Co. v. Blodgett, 260 U.S. 647, 652 (1923) (upholding a state statute retroactively imposing an estate tax and imposing a 2% penalty for non-payment, holding that the penalty “was not in punishment of a crime, and it is only to such that the constitutional prohibition applies” ). In Locke v. City of New Orleans, the Supreme Court denied an ex post facto challenge to a tax law, holding both that the law was not retroactive and that the Ex Post Facto Clause did not apply to the non-penal tax at issue. 71 U.S. 172, 173 (1866).

2

219 U.S. 140, 152 (1911).

3

Id. at 152–53.

4

97 U.S. 381, 381, 385 (1878).

5

Id.