In early September 2011, President Barack Obama rejected EPA’s draft rule to reconsider the 2008 ozone national ambient air quality standard (NAAQS) based on the OIRA’s recommendation. The letter from OIRA Administrator Cass Sunstein cites regulatory uncertainty and resulting implementation costs as reasons for its rejection, despite the fact that the CAA does not permit EPA to consider implementation costs in promulgating NAAQS. Based on the Supreme Court and D.C. Circuit jurisprudence on executive orders, such a presidential decision, inconsistent with congressional will, should be both subject to judicial review and found unconstitutional because it violates the separation-of-powers principle.