This chapter explores the development of the principle of non-refoulement beyond the Refugee Convention. In broad terms, this can be described as ‘complementary protection’ because the non-refoulement obligation derives from sources that are complementary to the Refugee Convention. However, though not a term of art, ‘complementary protection’ commonly implies the grant of a domestic legal status as well. Under general international law, the principle of non-refoulement is wider than its expression in article 33 of the 1951 Refugee Convention. While States have always recognized, to varying degrees, the protection needs of people falling outside the ‘refugee’ definition in article 1A(2) of the Convention, it is only in the last 25 years or so that they have begun to articulate such protection as an international legal obligation, rather than as a matter left to the discretion and humanitarian goodwill of national governments.