This thesis deals with the question of just and unjust violence and also compares approach to the just violence today and in the past. It presents comparison of systems of if-conception self-defense and MS-1 self-defense which comes from sindefendology. From this comparison is clear, why it is necessary to refuse all so called if-conceptions self-defense (jujitsu, aikijitsu, karate, kenjitsu or other similar systems). The two main sources of this thesis are sindefendology (science of self-defense) and Christian ethics. The criteria for ethical justification are following: St. Thomas Aquinas's Summa theologiae, Catechism of theCatholic Church and real possibilities of attacked person to defense (with regard to dangers, which come from the situation). It is necessary to distinguish between self-defensive and self-protective situations. This distinction helps to comprehend the nature of combat situation, and therefore also to choose the ethical acceptable actions on time. There are described some cases which shows importance of the knowledge of sindefendology about real possibilities of attacked person. Course of justice without the knowledge of sindefendology and ethics can be unjust for attacked man.