The paper is focused on the description and brief analysis of the events of the beginning of the Russian invasion of Ukraine from the point of view of international law. The paper deals with the role of the United Nations and the inability of the Security Council to fulfil in this case its basic function stemming from the UN Charter. The paper briefly describes the relevant aspects of law during armed conflicts, prohibited methods and means of warfare in relation to the war in Ukraine. The paper also deals with issues of investigation of non-compliance with the obligations of the Russian Federation arising from international law and the prosecution of the most serious crimes under international law.