The paper deals with some issues of the law of armed conflict in relation to the armed invasion of the Russian Federation against Ukraine. The paper is divided into two parts. The first part of this paper deals with the issues of illegal use of force by the Russian Federation, the role of the Security Council and the Ukrainian exercise of the right to self-defense. The second part deals with the use of prohibited means and methods of fighting in relation to attacks on the civilian population. The paper seeks to determine what specific (customary or contractual) rules of international law have been violated by the Russian Federation.