International law has been repeatedly challenged for its exclusionary character and its imperial uses. These critiques describe many of its structures and dynamics in a precise manner. However, international law may be a useful instrument for protecting the legitimate interests of the States of the Global South in general, and of the distinct social and cultural groups that form them, in particular. Yet, in order to understand international law's potential for emancipation or social resistance, it is necessary to complement theoretical critiques with the examination of concrete forms through which the Global South makes use of international law to resist or transform its social reality. However, this theorization must emerge, at least in part, from the particular experiences that social movements and organizations have had with the use of international law for the defense of their communities, their lands, and their natural resources. This article explores the ways in which international law may be used as a tool to protect the rights and natural resources of some of the most vulnerable groups in the Global South: indigenous peoples and culturally diverse black communities. This analysis proceeds by means of a case study. This chapter examines the strategic litigation project that began when a public action of unconstitutionality was brought before the Colombian Constitutional Court against the General Forestry Law (GFL), and that culminated with ruling C-075 of 2008 declaring the law unconstitutional. The analysis of this strategic litigation project is divided in two parts: the first part examines the way in which international law and national law are interwoven for the protection of the rights of Colombian cultural minorities and of the environment. The second part presents the legal and political arguments that explain why, in Colombia as well as in other countries of the Global South, international environmental law and the international law on cultural minorities may be (and are) used effectively in national courts.