303 © The Author(s) 2019 P. Engstrom (ed.), The Inter-American Human Rights System, Studies of the Americas, https://doi.org/10.1007/978-3-319-89459-1_12 CHAPTER 12 Impact in the African and Inter-American Human Rights Systems: A Perspective on the Possibilities and Challenges of Cross-Regional Comparison Frans Viljoen F. Viljoen (*) Centre for Human Rights, University of Pretoria, Pretoria, South Africa e-mail: Frans.viljoen@up.ac.za INTRODUCTION There are two main approaches to a cross- or inter-regional comparison of the impact of the Inter-American and the African human rights systems. The comparison may treat the two systems as distinct or discrete, and aim to draw ‘lessons’ or useful insights from one system to infuence (or ‘impact on’) the other system. One may, for example, analyse the charac- teristics of the ‘precautionary’ or ‘provisional’ measures mechanism, as developed by the Inter-American Commission on Human Rights (IACHR) and Inter-American Court of Human Rights (IACtHR), to serve as guide for the strengthening of this mechanism by the African Commission on Human and Peoples’ Rights (African Commission) and