This Chapter attempts to highlight the existence of a veritable cornucopia of uncharted areas in a treaty’s ‘life-cycle’ where a strictly legal approach is not sufficient and where PE/IPE can yield valuable insight. The law of treaties will be examined mainly through the lens of IPE, and as an explanandum (dependent variable), while methodologically the analysis for the most part, will be conducted under the second column of Kantorowicz’s epistemological trilogy , i.e. Realwissenschaft (sociological perspective). In the Section, however, ‘Evolutive Interpretation’ due to the very nature of that analytical part the third column will also be used, i.e. Normwissenschaft (doctrinal perspective). The Chapter does not purport to provide a complete list of all IPE approaches and tools to explain law of treaties in toto. This field of PIL is so open-ended and allows for adoption of so many different approaches in the design and functioning of treaties that any such exhaustive attempt would be an exercise in futility. For this reason, the aim is to highlight the fact that there is a multitude of areas of the law of treaties which have not yet been the subject of IPE analysis and to pinpoint those where IPE considerations, approaches and tools may or are needed to come into play in order to understand the outcome. Consequently, the content of this Chapter has been structured following a ‘from cradle to grave’ approach and the following areas have been selected for their instructional value: i) non-State determination of the existence of a treaty ii) evolutive interpretation iii) Normative conflict and iv) termination of treaties.