Weapons of mass destruction are the most destructive type of weapons and, due to their characteristics, they represent a real danger for the entire humanity because the issue of its legal regulation has not yet been completely resolved. Unlike biological and chemical weapons, which are regulated by international coventions, nuclear weapons, until recently, were not explicitly prohibited by any international legal norm. In this regard, in its Advisory Opinion of 1996 even the International Court of Justice was unable to take a definite stand on the question of whether the threat of use or the actual use of nuclear weapons in circumstances of self-defense is contrary to the rules of international humanitarian law. In that time period of 25 years, the law of armed conflicts as a segment of international law experienced numerous changes that occurred as a result of the efforts of the international community to establish a concrete legislative framework in order to reduce and limit the use of such weapons. A recent turning point occurred when the new Treaty on the Prohibition of Nuclear Weapons entered into force in 2021. Although at first it seems that, along with declared nuclear-weapon-free zones and the prohibition of nuclear tests, this Treaty might complete the legal regulation of weapons of mass destruction, the "rattling” of nuclear weapons during the Russian invasion on Ukraine raises the question of whether we are walking on the edge of a new nuclear war once again.