Yale Environmental Law Association invited David Farnsworth to discuss emissions trading schemes past, present, and future at their Climate, Markets, and Law event on October 18, 2013. Drawing on his experience with the Regional Greenhouse Gas Initiative (RGGI), he provided the practical perspective on regulatory best practices for emissions trading schemes. He emphasized the – often underestimated – value of energy efficiency as a climate and energy policy strategy. Not only are efficiency programs highly cost-effective, investments in efficiency yield a multitude of energy and non-energy benefits.