Robin Vander Wall
It’s very simple. Efficiency. The same reason that a mechanic will stop looking for a problem with your car when he has already found the issue you’re complaining about. There’s no point in going any further although there may well be other problems with the car.
The defendant appealed his outcome at trial. He made a constitutional challenge against the statute under which he was prosecuted. He presented two arguments. The Court dealt with the first argument and determined that he was entitled to relief. There was no reason for the Court to reach the second argument. This is standard judicial procedure. There is nothing other worldly about it. The fact that the Court declined to consider the ex post facto argument does not mean that the argument isn’t valid.
Pepitone successfully won in the IL COA by claiming that the statute was “facially invalid”…and he did that under a rational basis analysis. That’s a far greater victory than getting relief under an ex post facto claim.