Weapons will be readily available in the black market. The government has a difficult enough time keeping firearms out of the hands of prison inmates much less a free citizenry. Therefore if a man is not imprisoned for a crime, he retains the right to keep and bear arms. But there is a major difference between murder and providing oneself with the means of self-defense. The first is an immoral act involving the initiation of force against another person, owning a firearm is at the most an amoral act and within the context of Objectivism a morally dynamic act.
Murder is reprehensible, while self-defense is a highly moral act.
Furthermore, when a man is released from prison, if he has adopted a rational approach of dealing with other men, then he most vigorously needs the means of defending himself against his former cohorts who may try to force his old lifestyle upon him. Even an ex-convict must be presumed innocent. Free citizens must keep in mind that some human beings are dangerous, and arm themselves accordingly. Criminals released after serving their time are not the only danger. The Constitution of the United States of America was a wonderfully conceived document.