California, the world’s fifth-largest economy and 18th in total carbon emissions if it were a separate country, is rapidly moving forward with the development of its cap and trade program scheduled to be implemented in 2013. This has drawn a lot of attention from businesses generating high quantities of carbon emissions or who consume large amounts of energy or fuel. Carbon futures linked to Californian’s cap and trade program slipped recently, but after a test auction in late August 2012, news articles reported that major banks are weighing whether to wade into the California carbon market, which experts believe could grow into a $40 billion-a-year market by 2020. The California state legislature passed Assembly Bill 32 (AB 32) in September 2006 requiring the state to reduce greenhouse gases emissions to 1990 levels by 2020, a 17 percent reduction—and eventually to an 80 percent reduction by 2050. There are complications to the California cap and trade system that do not exist in other cap and trade programs to date. For example, California’s program covers all six “Kyoto” GHGs—a multi-gas-wrinkle that the EU-ETS will only be tackling in this, its third compliance period. Further, the California Air Resources Board (CARB) retains the ability to reverse trades of carbon offsets or credits in order to enforce holding limits under the CARB regulations. These will present unique challenges to compliance entities, as well as to the brokers, traders, suppliers, and others trying to create a new carbon market. To understand the basic underpinnings of the California cap and trade system, this Reed Smith Client Alert sets forth design elements of the system: the “what, who, when, and hows” of cap and trade under AB 32.