This paper examines international treaties in relation to the threat or use of nuclear weapons including the 1968 Nuclear Non-Proliferation Treaty and the 1996 Comprehensive Test Ban Treaty. it can be concluded that the effect of the aforesaid international treaties is still in doubt without explicit enforcement mechanisms and penalty for non-compliance. This paper also reviews the International Court of Justice's advisory opinion on the legality of the threat or use of nuclear weapons and comments that a clear explanation on the legality of use of nuclear weapons in 'extreme circumstances of self-defence' is required. Examples from current state practice in relation to nuclear non-proliferation efforts are also provided, with special attention to China, North Korea and Iran. This paper suggests that China as a leader of developing countries should extend its efforts on nuclear non-proliferation and conduct communication between North Korea and Iran and other nuclear weapons states to reduce or prohibit nuclear weapons. (C) 2009 Elsevier Ltd. All rights reserved.