[Bob J]

Ex post facto laws protect people from being criminally prosecuted after the fact, it has nothing to do with correcting badly written legislation or assisting the victims of immoral laws. According to your theory, only slaves AFTER the 16th amendment would be free.

You don’t have to be an attorney to realize this...but it helps.

[Cyropaedia]

Uh Bob... it was the 13th Amendment that banned slavery. And no, your analogy does not apply. The 13th Amendment did not apply "retroactively" it stated that effective immediately, slavery, as a practice/institution was explicitly banned by the Constitution. And as such, all slaves were now free.

Now, why don't you show us all the examples of a new criminal statutes being retroactively by Congress as to nullify actual verdicts rendered in criminal trials. I'm sure over the period of nearly 200 years there must be a vast multitude of examples/ precedents. A new criminal statute cannot be applied retroactively either to nullify verdicts after the fact or to prosecute people (after the fact). Such a precedent, if upheld, would unfortunately cut both ways.