This article analyzes the actions of international documents establishing the principles of territorial integrity and inviolability of states in modern conditions. Despite the fact that relations between the countries have international legal regulation, military conflicts in the world do not cease due to territorial claims. Most conflicts originate in the depths of centuries, in which it is difficult to recreate the true historical circumstances and assess the validity of the claim of one or another disputing party. The article analyzes conflicts arising from territorial disputes from the perspective of international law. Based on international legal norms, there are legitimate ways to change state borders. For example, the most common of them, in order to achieve a peace agreement that satisfies the disputing parties on the establishment of state borders, is a treaty. In addition, through purchase, lease, artificial increment, by secession from the country, or on the contrary, reunification, states can increase or decrease the borders of their territories. In the 90s, in connection with the collapse of the USSR, the so-called "parade of independent countries" began, which led to the formation of new states and related procedures for the delimitation and demarcation of borders. The establishment of borders took place in various conditions. If in some cases an agreement was reached without difficulty, in others, the arrival of a general consensus was delayed for decades, as in the example of the division of the Caspian Sea between five states. This procedure lasted 22 years and ended in 2018 with the adoption of the Convention on the Status of the Caspian Sea.