The term “indigenous” is not merely descriptive but shaped by structures of power, exclusion, and legal recognition. This paper interrogates how the non-recognition of local laws, customs, and traditional legal systems has produced marginalization that, paradoxically, comes to define indigeneity itself. Colonial and postcolonial legal orders have eventually displaced indigenous knowledge systems, replacing them with homogenized “mainstream” frameworks under the banner of codification, modernization, and national integration. Such processes have forced indigenous communities to reformulate their identities, rights-claims, and practices within state-sanctioned legal vocabularies stripping them of the heterogeneity. Drawing on critical studies and Third World Approaches to International Law (TWAIL), this paper explores the tension between formal recognition and epistemic erasure. It argues that mainstreaming through the process of garnering legal recognition is aimed towards homogenization and leads to marginalization resulting in erasure of the indigenous. Through references from Australia, Canada, India and Brazil, it terms “mainstreaming” of indigenous legalities as a double-edged sword offering visibility but often at the cost of assimilation. Thus, the paper vouches for the role of international law in regulating this process of homogenization in order to safeguard heterogeneity.