The Kyoto Protocol has been ratified by 164 states and is now fully operational. However, the Bush administration's repudiation of the Protocol combined with the weakness of the targets raise a confronting question for students of legitimacy: is it possible for a regime to be legitimate but ineffective in solving the problem it is designed to address? I argue that effectiveness is an important component of the Protocol's legitimacy but that the parties have been reluctant to make an issue of effectiveness during the early phase of the Protocol's operation. However, the legitimacy of the Protocol is likely to wane, and the chronic international legitimacy crisis of the Bush administration's climate change policy is likely to become acute, as a result of poor performance. I conclude by suggesting what might constitute significant and timely adaptation that might resolve the US's chronic legitimacy crisis and the Protocol's …