A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
The counstitution is the basis of the rights all people are born with. By virtue of their actions, followed by due process in a court of law; they have proven themselves unfit to enjoy the full benefits that the bill of rights extends. If they murder, they also lose some more rights, as they are in jail, and may be executed. Or are you suggesting that we just ignore criminals and let them legally obtain weapons just like the rest of us?