Actually, you don't have to. It's not that there is a prohibition against private ownership of firearms, it's just that Amendment II doesn't speak to private ownership.
The only time this would ever come up is in the extraordinarily unlikely event that the Congress passes a law banning private ownership. Unless the USSC wanted to reverse the precedent of Miller and at least two other cases I can think of off the top of my head subsequent to Miller (an unlikely, but not impossible track for them to take), it would rule the private ownership ban Constitutional.
Then you'd have something to bitch about :-)