After the already published book "Treaty Law of International Organizations, Emergence of the 1986 Convention", the present book focuses on special issues of international treaty law such as consultations, negotiations, the treaty, especially the multilateral treaty of universal character, the final acts, the codification of international law, the treaty-making process, jus cogens, the principle pacta sunt servanda, the clausula rebus sic stantibus, the pactum de consultando as a new terminus scientificus, coined for the first time here, the pactum de negotiando and the pactum de contrahendo.These topics were for many years part of the author's basic research as well as his special lectures on international law. Furthermore, some expert opinions, prepared by the author in his capacity as a governmental expert for the purposes of the UN, are used. UN documents as well as specialist literature in several languages and from various legal circles were evaluated.