If the 2nd Ammendment was interpreted by liberals the same way they interpret all the other Ammendments; every man, woman and child in the country would be required to not only own at least one firearm but also demonstrate proficiency with it on a regular basis.
That would come under Congress power to provide for arming the militia. The second amendment states what govenment may not do, while the militia powers of Art. 1 Section 8 and Art 2 Section 2 state what it can do. It can, and it has in the past, required ownership of arms and ammunition. It can also require demonstration of proficient.
Can you imagine all the wailing an knashing of teeth if it tried to exercise those powers today? Be fun to watch.
The Swiss have somewhat similar requirements, although they provide the weapon and ammunition, but the individual is required to keep it, and occasionally show some proficiency with it. And it's either an assault rifle, a battle rifle (for the older gents) or a pistol (for the officers). The individuals are free to practice as much as they wish with their issue rifle, although they can't shoot up the "ready ammo". They can purchase ammo, heavily subsidized, at a local range. Technically they are supposed to shoot up all they buy at the range, but they are free to buy commerical ammo at full price for their issue weapon. Wish it were that way here. I'd shoot my battle rifle more, and my 1911A1 a little less.