All the balls that are in motion towards regulation will now stay in motion. First, the endangerment finding, which is the foundation for all the regulation, is intact. That means that the vehicle rules finalized in March 2010 setting mileage and emissions standards for model-year 2012, which are the first ever to address GHGs [greenhouse gases], will go into effect in January.
Under EPA's interpretation, GHGs become "subject to regulation" on January 2, 2011, which is when the vehicle rules become operational. Once GHGs are subject to regulation, new stationary sources (i.e. smokestacks) that emit more than certain thresholds of GHGs will require permitting that mandates the "best available control technology" for GHGs.
Initially, in January, under EPA's "tailoring rule" only sources that emit more than 75,000 tons of will require permitting but only if they also require permitting for conventional pollutants as well. Then in July 2011, any facility that emits more than 100,000 tons of CO2e will require permitting even if they do not require a permit for conventional pollutants. EPA has not stated if or when they are going to lower the thresholds to smaller sources.