Its unconstitutional. The second amendment was not added primarily for personal protection, and so banning weapons because they don't fit into that restrictive purpose doesn't take into account the intent of the amendment which was to keep and bear arms in order to protect the State. Pistols are not so useful in that role anymore.
The signers knew that an armed society was was a major limiting factor in how much control the central government could impose. The biggest threat to freedom was known to be the government, the power capable of infringing on that right for the gain of politicians and others.
That being said, there's no reason armed citizens shouldn't be 'well regulated'. Background checks, waiting periods, training and qualifying are all reasonable regulations.