Discussion of policy approaches to reducing greenhouse gas emissions currently centers on emission trading, virtually to the exclusion of all other options. While trading has a place in the policy portfolio needed to mitigate global warming, it alone will not be sufficient. Although the Clean Air Act is not a perfect fit for the problem of climate change, its cooperative federalism framework can help fill the gaps left by an emission trading strategy. A mandate, modeled on the State Implementation Plan program, that states inventory emission sources and meet emission-reduction targets is better suited than markets to motivate behavioral change. Technology-based regulation, with minimum standards set at the federal level but one or more states allowed to impose more stringent standards, can better drive innovation. In crafting federal climate change legislation, Congress should look to tailor these elements of the Clean Air Act to the greenhouse gas problem, rather than tossing them out in favor of a strictly market-based approach.