From the WSJ (source):
Mr. Crocker sees two modern-day problems in using a cap-and-trade system to address the global greenhouse-gas issue. The first is that carbon emissions are a global problem with myriad sources. Cap-and-trade, he says, is better suited for discrete, local pollution problems. “It is not clear to me how you would enforce a permit system internationally,” he says. “There are no institutions right now that have that power.”
All of you politicoterryians out there in the Terryverse: discuss!