The Environmental Protection Agency (EPA) is removing the "emergency" affirmative defense provisions from the EPA's title V operating permit program regulations. These provisions established an affirmative defense that sources could have asserted in enforcement cases brought for noncompliance with technology-based emission limitations in operating permits, provided that the exceedances occurred due to qualifying emergency circumstances. These provisions, which have never been required elements of state operating permit programs, are being removed because they are inconsistent with the EPA's interpretation of the enforcement structure of the Clean Air Act (CAA or the Act) in light of prior court decisions from the U.S. Court of Appeals for the D.C. Circuit. The removal of these provisions is also consistent with other recent EPA actions involving affirmative defenses and would harmonize the EPA's treatment of affirmative defenses across different CAA programs. Through this document, the EPA is also providing guidance on the implementation process resulting from the removal of the emergency affirmative defense provisions from the EPA's regulations, including the need for some state, local, and tribal permitting authorities to submit program revisions to the EPA to remove similar title V affirmative defense provisions from their EPA-approved title V programs, and to remove similar provisions from individual operating permits.