EPA issued the Cross-State Air Pollution Rule (CSAPR) in 2011 to address interstate transport and to replace the Clean Air Interstate Rule (CAIR), which the D.C. Circuit had remanded to EPA for action. CSAPR requires 28 states to limit emissions of sulfur dioxide (SO2) and/or nitrogen oxides (NOx).

Industry and government petitioners challenged CSAPR in the D.C. Circuit and sought a stay of the rule pending judicial review. The court granted the stay on December 30, 2011 and ordered EPA to continue administering CAIR on an interim basis until a final decision was reached on the validity of CSAPR. Subsequently, the D.C. Circuit vacated CSAPR, but the U.S. Supreme Court reversed that decision. Following the Supreme Court decision, EPA moved to lift the stay of CSAPR, and the D.C. Circuit granted the motion in October 2014.

To address implementation issues resulting from the stay, EPA adopted ministerial amendments in December 2014. Compliance with the CSAPR Phase I emissions budgets was required in 2015 and 2016 (instead of 2012 and 2013 in the original rule). Compliance with the Phase II emissions budgets and provisions was adjusted to 2017 and beyond (instead of 2014 and beyond). The amendments also tolled deadlines for other requirements such as reporting, sunsetting of CAIR-related obligations and removal of CAIR NOx allowances from tracking system accounts. The December action was considered an interim amendment.

On March 14, 2016, EPA published a final rule in the Federal Register to make the interim changes permanent. EPA rejected various comments including comments opposing any tolling of the original deadlines, comments requesting that the deadlines be tolled for four rather than three years and comments asking that certain unit level allocations be adjusted.