In 2002, EPA promulgated a Clean Air Act new source review (NSR) “reform rule” to clarify the confusion created by inconsistent guidance and judicial decisions on NSR applicability.  That clarification effort had only limited success, as inconsistent interpretations of the NSR applicability rules continued to emerge as those rules were applied by state regulators and courts.  In perhaps the most extreme example of regulatory confusion, a three judge panel of the Sixth Circuit issued five opinions with three different interpretation of the same regulatory language.  DTE I, http://www.opn.ca6.uscourts.gov/opinions.pdf/13a0080p-06.pdf.  DTE II, http://www.opn.ca6.uscourts.gov/opinions.pdf/17a0006p-06.pdf.

The Trump Administration has embarked on a new clarification effort.  In what EPA’s Office of Air and Radiation dubbed a “singles and doubles” approach, EPA issued guidance and undertook rulemaking on key applicability issues, including emissions projections, emissions accounting, and project aggregation.  In conjunction with the Affordable Clean Energy rule, EPA then proposed a more fundamental change to the NSR applicability rules under which a project would trigger NSR only if it resulted in both an hourly and annual emissions increase.

That EPA is still struggling with clarification of its NSR rules two decades after it began a series of significant NSR enforcement initiatives illustrates how controversial this program has been and continues to be.  From an environmental standpoint, however, the NSR program has become less significant. Industrial sources are largely well-controlled for a variety of reasons other than NSR.  And in the electric utility sector, the steep drop in the price of natural gas has resulted in current or planned retirement of many coal-fired generating units.  As a result, there is little to be gained from injunctive relief even in a successful NSR enforcement action.

All of this says that there should be wide-spread support for EPA completing its NSR clarification efforts.  Regulated entities have every incentive to comply with NSR.  From the regulators standpoint, the limitations the Supreme Court put on regulatory re-interpretation in Kisor v. Wilkie, should create its own incentives for regulatory clarity.