In a very complex, hard-fought case, U.S. District Judge David Hittner discusses how the Texas Commission on Environmental Quality’s (TCEQ) regulatory affirmative defenses to alleged Clean Air Act (CAA) violations will be viewed by the courts, if not the regulatory agencies. Environment Texas Citizen Lobby, Inc., et al., v. ExxonMobil Corp., et al. involves the complex regulatory regime that any large industrial facility must follow—whether it is a chemical plant, a refinery, steel mill, automotive assembly plant— if they have air emissions that must be regulated. In addition, these facilities must adhere to strict reporting rules, where evidence of non-compliance can often be found by litigants without a lot of hard work. A defense to some of these complaints lies in the fact that regulatory authorities will exercise prosecutorial discretion—by rule—when no one can control emissions during an unplanned upset (i.e., accident, natural disaster, etc.) or a planned shutdown for plant maintenance. ExxonMobil’s “Act of God” defense might have worked, it seems, if Texas had properly incorporated that state requirement in its federal State Implementation Plan (SIP). It should be noted that large scale construction projects necessitate many state and federal permits, and now there are federal laws and regulations to expedite the federal review—and new Executive Orders to reinforce that policy.