Don't be too specific with your geographic element in the subject searches - try Africa, Southern & Africa to find relevant chapters
Indigenous peoples -- Legal status, laws, etc. -- [geographic unit]
Indigenous peoples -- Civil rights -- [geographic unit]
Indigenous peoples -- Land tenure -- [geographic unit]
We Want What's Ours: learning from South Africa's land restitution program by 
Land, power & custom : controversies generated by South Africa's Communal Land Rights Act by SOLO searches will probably reveal that other parts of the Bodleian - such as the Bodleian Social Science Library,
Bodleian Social and Cultural Anthropology Library, and the Bodleian Closed Stacks have useful texts on the topic topic too!
Indigenousness in Africa : a contested legal framework for empowerment of 'marginalized' communities by 
Land Rights of Indigenous Peoples in Africa by Related Bodleian Law Library Guides