Thomas Aquinas

“ But he who presides over a community of the first kind, can inflict only corrective punishment, which does not extend beyond the limits of amendment, and these are exceeded by the punishment of death. Wherefore the husband who exercises this kind of control over his wife may not kill her, but he may accuse or chastise her in some other way.
Art. 2 - Whether wife-murder is an impediment to marriage? Objection 1: It would seem that wife-murder is not an impediment to marriage. For adultery is more directly opposed to marriage than murder is. Now adultery is not an impediment to marriage. ”

“ But the Church is not bound in this matter by human laws, neither does she acquit him of the debt of eternal punishment, nor of such punishment as may be awarded him by an ecclesiastical tribunal for the reason that he is quit of any punishment to be inflicted by a secular court. Therefore in no case is it lawful for a husband to kill his wife on his own authority. ”

“ He is not however hereby rendered simply unfit by law in relation to other women: wherefore if he should have married another, although he sin by disobeying the Church's ordinance, the marriage is nevertheless not voided for this reason. ”

“ Accordingly, he who presides over the latter kind of community, a king for instance, can punish an individual both by correcting and by exterminating him, for the betterment of the community with whose care he is charged. ”