This report is dedicated to some questions concerning establishment of rules and limits of criminal liability for participation in war crimes. According to results, any State will be held responsible for aiding or abetting another State in the commission of an international harmful act, or for knowingly inciting such a wrongful act. A State could be charged for aiding or abetting paramilitary groups for war crimes even if such groups do not take part from state regular forces, but they receive instructions, guidance or control in order to commit criminal acts. The territorial distance of the accomplice from the scene of the crime assumes that the mental attitude of the offender must cover such misbehavior. If the offender was aware about the ongoing crime and, despite this, provided assistance, then his assistance is directed to a certain crime. The posting of educational videos on social networks, in which mentors explain and instruct a potentially unlimited number of people, for example, how to create, collect, apply and perform other similar acts in order to activate means and tools that have a damaging property, should be recognized, depending on the circumstances of the case, as training in terrorism or as complicity in the commission of war crimes, armed rebellions, riots, etc.