In today's action, EPA is temporarily staying, until November 30, 1999, the effectiveness of a final rule regarding petitions filed under section 126 of the Clean Air Act (CAA). Eight Northeastern States filed the petitions seeking to mitigate transport of one of the main precursors of ground-level ozone, nitrogen oxides (NO<INF>X</INF>), across State boundaries. On April 30, 1999, EPA made final determinations that portions of the petitions are technically meritorious. Subsequently, two recent rulings of the U.S. Court of Appeals for the District of Columbia Circuit (D.C. Circuit) have affected EPA's rulemaking under section 126. In one ruling, the court remanded the 8- hour national ambient air quality standard (NAAQS) for ozone, which formed part of the underlying technical basis for certain of EPA's determinations under section 126. In a separate action, the D.C. Circuit granted a motion to stay the State implementation plan (SIP) submission deadlines established in a related EPA action, the NO<INF>X</INF> State implementation plan call (NO<INF>X</INF> SIP call). In the April 30 notice of final rulemaking (NFR), EPA had deferred making final findings under section 126 as long as States and EPA remained on schedule to meet the requirements of the NO<INF>X</INF> SIP call. In response to these rulings, EPA is today staying the effectiveness of the April 30 NFR for a short period while EPA conducts a notice-and-comment rulemaking to address further issues arising from the court rulings.