In Advisory Opinion OC-18 of September 17, 2003, the Inter-American Court of Human Rights ruled that international principles of nondiscrimination prohibit discriminating against undocumented migrant workers in the terms and conditions of work. The Court acknowledged that governments have the sovereign right to deny employment to undocumented immigrants, but held that such workers are equally protected by human rights in the workplace once an employment relationship is initiated. In other words, states may not further their immigration policies by denying basic workplace protections to undocumented employees.
Sarah H. Cleveland,
Legal Status and Rights of Undocumented Workers: Advisory Opinion OC-18,
Am. J. Int'l L.
Available at: https://scholarship.law.columbia.edu/faculty_scholarship/2621