Abstract: This paper makes a case for equality of competitive opportunity between Mexican and other immigrants from regions south of the United States border on the one hand, and similarly-situated immigrants from other regions, particularly Asia and Africa, on the other hand. Towards this end, the paper argues that the United States risks a violation of its WTO obligations, notably the Most Favoured Nation (MFN) obligation, in the way it has gone about or will go about enforcing its immigration laws under an open borders immigration regime. Specifically, the debate about open borders in the United States has largely focused on the United States’ southern border and nearby ports with proponents arguing, implicitly or explicitly, for reduced enforcement of immigration measures in the region. The net effect of this would be to allow greater access into the United States for Mexican, Central American and Caribbean migrants who are, in trade terms, exporters of Mexican, Central American and Caribbean services into the United States, while failing to offer the same level of opportunity for access to similarly situated (like) migrants from countries that do not share borders with, or have near access by land or sea to the United States such as migrants from Asia and Africa. This would violate the MFN principle and justify WTO action against the United States since The WTO’s General Agreement on Trade in Services (GATS) obliges the United States to provide equal access to US markets for exports of services from WTO member countries. For an open borders policy to survive legal challenge under WTO disciplines, it would be necessary for the United States to devise ways of restoring the competitive equilibrium between migrants from countries contiguous to or near the southern borders and those from countries that do not share borders with or have near access by land or sea to the southern borders.