spat
.700 Nitro Express
No, that is not an appropriate comparison at all.Sadly, cops are often put between a rock and a hard place. If you're following an order yoy believe to be lawful (whether you agree with it or not), and its later deemed unlawful, that's a similar scenario to ex post facto if you're punished for it.
Ed post facto is about retroactively making something illegal.
This would be something that was always illegal and the officer was just mistaken.
"ignorance is no excuse" is what they'll tell you.
Just like the poor guy who thinks his Virginia permit will let him bring his handguns to his buddy's house in NY.