 But by far her most-cited contribution to administrative law is her 2004 judgment in "Bato Star v Minister of Environmental Affairs and Tourism", which sets out South African law's approach to reasonableness review and judicial deference.O'Regan's judgment in "ACDP v Electoral Commission", dealing with the African Christian Democratic Party's application to contest the 2006 local government elections, introduced the doctrine of substantial compliance into South African law.Her judgment in "Richter v Minister of Home Affairs", also on political rights, extended the right to vote to South African citizens living abroad.