At a minimum, you want to have available weapons which provide a significant deterrent to government abuse of power. You want such abuses to be at the risk of a

At a minimum, you want to have available weapons which provide a significant deterrent to government abuse of power. You want such abuses to be at the risk of a protracted deadly fight that threatens the stability of the power of the abusive government. Anything beyond that is unnecessary, and too much beyond that threatens the security of the people as a whole. Practically speaking, I would allow everything up to .50 caliber machine guns with minimal regulation.