Ps are both non-profit organizations dedicated to the advancement and operation of non-professional high-powered rocketry and to the promotion of safety and education for sport rocket hobbyists (rocketeers). They have approximately 9,000 members. Sport rocketry involves the design, construction, launch, and recovery of aero-vehicles that ascend into the air using rocket motor engines generally containing more than 62.5 grams of ammonium per chlorate composite propellant (APCP) as the fuel source. On April 20, 1994, D wrote a letter to Aerotech, Inc. (Aerotech), one of the manufacturers of APCP, stating that APCP was an 'explosive' because it had been on ATF's annual 'Explosives List' since the list was first published in 1971. Aerotech had requested clarification regarding how Aerotech's business would be regulated under the 'Federal Firearms and explosives laws.' D indicated that a fully assembled rocket motor qualifies for the 'propellant actuated device' exemption, but prior to its assembly in a rocket motor, the propellant itself (the individual APCP module) is not covered by the 'propellant actuated device' exemption. D also indicated that this exemption only covered rocket motors that contain 62.5 grams or less of APCP. On February 4, 1999, Ps sought clarification for the basis and extent of ATF's regulation of the high-powered sports rocketry hobby. On November 24, 1999, a representative of D contacted counsel for Ps and stated that D 'finally and categorically' rejected Ps' conclusion that ATF's annual explosives list was both procedurally and substantively defective. Ps brought this case to obtain judicial review of D's actions pursuant to Section 10 of the Administrative Procedure Act (APA). D seeks the dismissal. Ps claim D lacks statutory authority under§ 841(d) (1994) to civilly regulate APCP.