This paper explores how firms respond to the Kyoto Protocol. In evaluating the impact of international institutions, the prior literature tends to emphasize the importance of administrative enforcement in inducing compliance. Using electric power companies’ greenhouse gas emissions data around the world, this paper finds that for international environmental agreements, administrative enforcement may not be as important as previously thought. Between 2004 and 2009, among the countries that joined the European Union more recently, political and economic considerations seemed to have played a greater role in bringing about reductions in greenhouse gas emissions than formal enforcement of the EU-Emissions Trading Scheme. Also, even without strong enforcement, the Kyoto Protocol appear to have pointed in the direction of environmental improvement in countries that ratified the Kyoto Protocol, allowing firms to take advantage of low hanging fruit opportunities. Firms with high pollution intensity were more responsive to the Kyoto Protocol than those with low pollution intensity. The use of voluntary programs such as the UN Global Compact, however, does not have any significant impact on corporate greenhouse gas emissions.