Utilities affected by the rule have been presented with five different sets of allowance allocations since July 2010. Some states have been "in" the group covered by the rule, then out, or vice versa. Allowances aren't the only aspect that has changed. Assurance provisions, which limit the amount of trading a state can do without being heavily penalized, have also gone through several iterations.
Additionally, since the CSAPR is based on helping downwind states comply with ozone and Pm2.5 National Ambient Air Quality Standards (NAAQS), as the NAAQS limits are lowered, it is likely that the CSAPR allowance allocations will be reduced as well.
The Greenhouse Gas Tailoring Rule is currently in litigation. While it is doubtful that the underlying endangerment finding will be revoked, if the court decides EPA overstepped its authority by eliminating smaller sources from regulation, the resulting universal applicability will overwhelm both state agencies and industry.
The Mercury and Air Toxics Standards (MATS) are likewise still facing legal challenges. And, no one knows quite where regulations for coal combustion residues and cooling water intake and discharge systems [316(a) and (b)] are going to end up. (Power Engineering, April 2012)