No you're wrong. Once an actual verdict is rendered in a criminal trail the case has to follow through the appeals process if the defendant(s) want the sentence overturned.
You can't apply a new (criminal) law retroactively for the expressed purpose of nullifying actual verdicts rendered in actual trials. Such a maneuver constitutes a violation of the Constitution's prohibition against ex post facto laws as well a violation of Constitution's separation of powers mandate. You don't have to be an attorney to realize this.
Now please provide the actual names of these attorneys here at FR that claim that such a maneuver is actually possible and the posts were they actually say so.
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.