Convention on the Elimination of All Forms of Racial Discrimination 1965, art 3 includes ‘States Parties particularly condemn racial segregation and apartheid and undertake to prevent, prohibit and eradicate all practices of this nature in territories under their jurisdiction.’
Commentary
Racial Segregation and the Origins of Apartheid in South Africa,1919-36 by 
Politics by Other Means: Law in the Struggle against Apartheid, 1980–1994 by 
Segregation and Apartheid in Twentieth Century South Africa by