Lockean rights: Each person has the right to do whatever she chooses with whatever she legitimately owns so long as she does not violate the rights of others not to be harmed in certain ways—by force, fraud, coercion, theft, or infliction of damage on person or property. Each person has the right not to be harmed by others in the mentioned ways, unless she voluntarily waives any of her rights or voluntarily transfers them to another or forfeits them by misconduct. Also, each adult person is the full rightful owner of herself and each child person has the right to be nurtured to adult status by those responsible for her creation. It is generally supposed in the Lockean tradition that they start from the premise of self-ownership.
In all Utopian justice systems people are considered to own themselves. Others cannot damage or control their bodies. They likewise cannot damage or control the bodies of others. High tech means to identify and capture a psychopath are preferred to teaching members of society or government to behave themselves in the manner of a psychopath. Acting like a psychopath towards a psychopath is not justified or permitted. Homicide is not legal for the state, the citizens or outsiders.
Euthanasia, however, is permitted. So if a person really wishes to be euthanized and has been warned by people that have been authorized by a judge, he should not switch off the safety on his gun. It seems like a small thing, but stupid people should not, by themselves, make the decision to commit homicide for any reason. Euthanasia is authorized by a judge and requires that the person to be euthanized submit voluntarily by threatening the life of another and by not surrendering his weapon when asked.
There should be a means of electronically disabling weapons in schools and public places. Guns should ping a cellular tower so that their location can be followed. Multi-shot weapons should not be licensed. People should have an identifying chip so that they can be found by the police if they cause another significant harm (it’s better than shooting them if they run)! Guns should be disabled if they are not held by the owner (the police and others should not have to shoot someone because they feel their gun may be taken away).