In recent years, the international legal order has evolved amid tensions arising from the process of globalization and the transformations of international society, in which the maximum political and military power is held by a superpower. On this basis this book aims to show, in a scientifically rigorous way but taking into account the target audience, mainly university students, which are the organization and basic structure of the legal order of the International Community. Progressively, this Community has become the holder of legal interests protected by International Law and the advances of such protection have led to very important legal changes such as the formation of peremptory norms of general International Law and the important development of normative sectors such as Law. Imternational responsibility of the State for wrongful acts, International Environmental Law and International Criminal Law. All these changes and the codification processes that have been progressively reflected, especially by the International Law Commission, are especially attentive to this new edition; Special attention is also paid to the current situation of the regulation of the use of armed force by States, which has suffered the negative impact of the Iraq war. In the midst of these contradictions, the Universal International Community maintains, nevertheless, the unity of its juridical order and a certain international justice finds its way in the struggle against fundamentalisms, nationalisms and hegemonisms that seek to realize their own selfish interests, sacrificing human rights and the fundamental freedoms of the person, the Rule of Law and democratic progress. Within this horizon of possible justice and great real difficulties, International Law shines as an indispensable instrument to protect international peace and security and the dignity of the person.