Yeah, but.... the leftists could have done that already under Obama. They didn't because of the obvious reason. We (their opposition) are very well armed and equipped to resist them (and pissed off just enough to start a revolution if they tried to pull something like that).
Besides... becoming a "convicted felon" would take time, court costs and taxpayer money (lots of it) for them to convict all gun owners who disobeyed an unconstitutional law. I really don't think that even the rabid leftists dare go that far.
A conviction isn't really necessary if they can bankrupt you through lawyer's fees and dragged out proceedings. Ask any of the bikers arrested at Twin Peaks in Waco. There are other ways to disenfranchise people.Crushing them economically doesn't even require a good case, just a willing prosecutor.