The goal of the Chapter is to examine how the Political Economy (PE) analysis may help international lawyers in addressing and solving traditional issues they routinely confront, concerning the formation, existence, change, extinction, interpretation of Customary International Law. Because of the relevant role each interpreter – lawyers, government executives, municipal and International judges etc. – plays for these various purposes, customary law is an area where the approach/methodology applied may make a difference. The Chapter deals with each of the above mentioned issues, as well as with the notion of State as conceived in PE, to conclude that while PE can offer a valuable set of instruments for some issues, like the regime of erga omnes obligations or interpretation, in the end its overall contribution is limited. More particularly, PE does not appear to provide tools to anticipate when States are likely to commit breaches. Also, the notion of States in PE may not be directly relevant in international law, due to a precise choice by this system in identifying the entities accountable in law.