The understanding on how international law is regulated is essential to be understood. There are many regulations, especially in international sphere that regulate states. This book captures the most fundamental rules on international law that needs to be understood by anyone who wishes to study about international law. The book is divided in three chapters. The first chapter discuss The Covenant of the League of Nations. In the second chapter, the author describes about The Montevideo Convention on the Rights and Duties of States. Meanwhile, in the third chapter, the author discussesthe United Nations Charter. In each chapter, there are four parts that assist the understanding of those regulations which are the introduction, substance of the regulation, the importance of the regulation, legal terms identification, and the text of the regulation itself.