 In 1999–2000 and 2001 he was fellow at the Max Planck Institute for Comparative Public Law and International Law, Heidelberg.He was a visiting professor at the University of Hong Kong and the City University of Hong Kong in 1993, 1994, 1995, 1998, 2000 and 2005, Kansai University, Osaka in 2002, National University of Singapore in 2005 and Jawaharlal Nehru University, New Delhi in 2006.In 2002–03 he was fellow at the Institute for Advanced Study, Berlin and in 2004, at the Indian Institute of Science, Bangalore.