The 'flexibility mechanisms' of the Kyoto Protocol - the emissions trading system (Article 17), joint implementation (11) (Article 6), and the clean development mechanism (CDM) (Article 12) - form together some of the most interesting aspects of the agreement. They represent, for the first time in an international environmental treaty, the wholesale utilization of market-based mechanisms for environmental ends. If implemented fully, they should lead to the creation of an entirely new global market, in the right to emit (and the commitment to control) greenhouse gases.