On February 7, 2013, the RGGI states released a revised RGGI Model Rule after a comprehensive program review that spanned 2012. Each state must now amend their existing RGGI regulations and/or secure legislative approval to adopt these amendments before January 1, 2014. The most significant change to the cap and trade program is a reduction in the current regional CO2 emissions cap by 45 percent from 165 million tons to 91 million tons. The revised cap level presents 2012 reported emissions. Other RGGI Model Rule provisions include: a methodology to adjust the RGGI cap to account for the private allowance bank of 2009-2013 vintage allowances, a cost containment allowance reserve, interim compliance periods, a simplified auction reserve price, simplified carbon offset provisions, and the addition of a forestry carbon offset project category. This issue brief provides background on RGGI and summarizes key changes to RGGI Model Rule.