The issue of humanitarian intervention and debates about it have become one of the most controversial questions in contemporary 'ius ad bellum'. The aim of the article is to discuss a validity of humanitarian intervention in the context of just war tradition. The prohibition of the threat or use of force contained in Article 2(4) of the United Nations Charter, is currently the subject of fundamental disagreement. There is comparable agreement neither states nor scholars on the exact scope of the prohibition. Controversies especially concern so-called 'unilateral humanitarian intervention', that is use of force in pursuit of human rights without express authority from the Security Council. The author argues that just war tradition seems to be an useful tool for solving difficulties surrounding the issue of validity of humanitarian intervention. The just war tradition offers a coexistence of two fundamental values of the international society, that is justice and peace. According to this tradition peace cannot be established without justice, and vice versa justice cannot exist without peace. That is why the tradition can serve as a medium protecting both human rights and international peace and security. Thus one can speak of a 'new life' of the just war tradition in today's international law.