The Law of the Earth guarantees every person the right to genuine self-defense, and gives everyone the duty to protect another who is under attack, especially one unable to defend themself. It lists the Right to Defense among the basic human rights.
What the Law regulates is not the tool but its use. Force is lawful only in defense against harm, and only in proportion to the harm it answers. Anyone who uses force, armed or not, is accountable for it, and can be called to rational arbitration to prove it was justified.
Some objects are contraband: anything whose principal function, in theory or in practice, is to violate the Law. The Law names nuclear, chemical, and biological weapons, cluster munitions, and land mines, because they can't be used without harming the innocent. (Title 1: Contraband.)
And no badge or uniform grants anyone the authority to use force that would be unlawful for anyone else. (Title 4.)