Editors' Summary: CERCLA §113(h), with some exceptions, prohibits legal challenges to response actions until the cleanup at a Superfund site is completed. While the section's sponsors hoped to prevent potentially responsible parties (PRPs) from using such challenges to delay their financial responsibilities, several federal courts have held that §113(h) also bars citizen suits brought to enforce the FWPCA, RCRA, and other environmental laws at Superfund sites. Such holdings seem counter to Congress' provision in §302 that CERCLA not affect or modify in any way obligations or liabilities under other environmental laws. This Article argues that the application of §113(h)'s jurisdictional bar to citizen suits may exempt the nation's worst pollution problems from most environmental enforcement. It presents the paradigmatic application of §113(h) in a discussion of the McClellan Air Force Base litigation and surveys the divided case law on the section's proper interpretation. The Article next reviews CERCLA's legislative history and argues that while Congress, in enacting §113(h), sought to prevent PRPs from interfering with cleanup activities, it did not intend to bar or delay enforcement actions against ongoing environmental violations. It argues that this interpretation is supported by EPA's view that RCRA enforcement actions, for example, are not inherently incompatible with CERCLA cleanup actions. Finally, the Article discusses whether §113(h)'s jurisdictional bar applies after the listing of a Superfund site on the NPL or after the initiation of a remedial investigation and feasibility study. The Article concludes that the listing of a site on the NPL may be a double-edged sword, because plaintiffs contemplating environmental enforcement actions at a polluted site may see their case evaporate if the site is subsequently listed.