The same divine authority that forbids the killing of a human being establishes certain exceptions, as when God authorizes killing by a general law or when He gives an explicit commission to an individual for a limited time.
Saint AugustineDrunkenness is a flattering devil, a sweet poison, a pleasant sin, which whosoever hath, hath not himself, which whosoever doth commit, doth not commit sin, but he himself is wholly sin.
Saint Augustine