The sentiment that ex post facto laws are against natural right is so strong in the United States, that few, if any, of the State constitutions have failed to proscribe them. ...The federal constitution indeed interdicts them in criminal cases only; but they are equally unjust in civil as in criminal cases, and the omission of a caution which would have been right, does not justify the doing what is wrong. Nor ought it to be presumed that the legislature meant to use a phrase in an unjustifiable sense, if by rules of construction it can be ever strained to what is just.
Thomas Jefferson, Letter to Isaac McPherson, August 13, 1813