1. A statute which simply authorizes the imposition of a tax
according to a previous assessment is not retrospective.
2. Every retrospective act is not necessarily an ex post
3. Such laws embrace only such as impose or affect penalties or
The Legislature of Louisiana enacted, A.D. 1850:
"That each of the municipalities of said city shall be and is
hereby empowered to levy a tax on capital on the assessment roll
for the year 1848, and a tax on capital on the assessment roll for
the year 1849, provided
that the taxes on capital on said
assessment rolls for the years 1848 and 1849 shall not exceed the
amounts already imposed by existing ordinances of the said
Under the authority of this act, the City of New Orleans, having
levied a tax on capital owned and employed during
Page 71 U. S. 173
the years mentioned by Locke, brought suit to enforce its
payment. One defense set up was that the act was unconstitutional.
The supreme court of the state having, on appeal from the district
court, whose judgment it affirmed, decided that it was not, the
case was now brought here for review.
MR. JUSTICE FIELD delivered the opinion of the Court.
The Legislature of Louisiana in 1850 passed an act authorizing
each of the municipalities of the City of New Orleans to levy a tax
on capital within its limits on the assessment rolls of 1848 and
1849 not to exceed the amounts imposed by existing ordinances. The
present action was instituted to recover in part the amount of the
tax levied under this act upon capital owned and employed by the
defendant in one of the municipalities. As a defense, the
defendant, among other things, alleged the unconstitutionality of
the act of the legislature authorizing the tax. The district court,
in which the action was brought, gave judgment for the city, and
the supreme court of the state affirmed the judgment.
The unconstitutionality of the act was asserted from its
supposed retroactive operation upon the notion that the prohibition
of the federal Constitution upon the states to pass an ex post
law extended to all retrospective laws.
There was nothing in the position taken which entitled it to
consideration. In the first place, the act was not subject to the
imputation of being retrospective. It did not operate upon the past
or deprive the party of any vested rights. It simply authorized the
imposition of a tax according to a previous assessment. In the
second place, even if the law had been strictly retrospective, it
would not have been within the constitutional inhibition. Ex
post facto laws
embrace only such as impose or affect
penalties or forfeitures; they do not include statutes having any
other operation. The term ex post facto,
construed, would apply to any act
Page 71 U. S. 174
operating upon a previous fact, yet the restricted sense stated
is the one in which it has always been held. It was the sense in
which it was understood at the time the Constitution was adopted,
both in this country and in England. *
* Blackstone 46; Calder v.
3 Dall. 390.