Viljoen, FransMurray, Rachel H.2025-10-212025-10-212024-02Viljoen, F. & Murray, R. 2024, 'What a difference do 20 years make? The impact of the core UN human rights treaties on the domestic level in selected states between 1999 and 2019', The Impact of the United Nations Human Rights Treaties on the Domestic Level: Twenty Years On: Second Revised Edition, pp. 1-32.978-90-04-37765-310.1163/9789004377653_002http://hdl.handle.net/2263/104789This introductory chapter provides a background to a collection of chapters discussing the impact of the core United Nations (UN) human rights treaties at the domestic level during the 20 years between 1 July 1999 and 30 June 2019. This is a follow- up to the study by Christof Heyns and Frans Viljoen, conducted with the assistance of country- based researchers, and published as The Impact of the United Nations Human Rights Treaties on the Domestic Level.1 In that study, Heyns and Viljoen aimed to track and understand the impact of the core UN human rights treaties during the 30 years between the entry into force in 1969 of the first of these treaties (the 1965 Convention on the Elimination of All Forms of Racial Discrimination (cerd)) and 30 June 1999.en© Frans Viljoen and Rachel Murray, 2024. This is an open access chapter distributed under the terms of the CC BY-nc-nd 4.0 license.United Nations (UN)TreatiesImpactStatesBook chapter