The present Article inquires whether a right to unilateral non-colonial (UNC) secession is grounded in the United Nations (UN) law of self-determination. The Article argues that peoples subjected to deliberate, sustained, and systematic human rights abuses in extremis (e.g., ethnic cleansing, mass killings, or genocide) by the existing state have an international customary law right to UNC secessionist self-determination. This right is coextensive with the “remedial-rights-only” philosophical approach to UNC secession. The Article further argues that in the post-millennial era two developments are likely for the law of UNC secessionist self-determination: first, the right will become available in response to human rights abuses in moderato (political, cultural, or racial discrimination); and second, in the much longer term, the right will become justified not only on remedial grounds but also on liberal philosophical bases. The latter development is predicted to parallel the increase in the number of liberal democratic governments throughout the twenty-first century.