CAA CO2 Journey

The path from "CO2 is not regulated" to "EPA regulates CO2 under the Clean Air Act" took 25 years, three Supreme Court cases, and a regulatory journey that illustrates how administrative law bends slowly but consequentially. Each step built on the last, and understanding the sequence explains why EPA's authority is both established and fragile.

Step 1: The petition (1999). Environmental groups petitioned EPA to regulate CO2 from vehicles under CAA Section 202. The Bush EPA denied the petition, arguing CO2 was not an "air pollutant" under the Act and that regulating it would conflict with other policies.

Step 2: Massachusetts v. EPA (2007). The Supreme Court ruled 5-4 that CO2 is an air pollutant under the CAA and that EPA must determine whether it endangers public health. This forced EPA's hand: it could no longer claim lack of authority.

Step 3: The Endangerment Finding (2009). Obama's EPA found that CO2 and five other greenhouse gases endanger public health and welfare. This finding, never rescinded despite attempts, is the legal foundation for all subsequent CO2 regulation under the CAA.

Step 4: Regulatory programs. EPA issued vehicle emissions standards (2010-2012), new source performance standards for power plants (2015, Clean Power Plan), and replacement rules (2019, ACE Rule). Each was litigated.

Why hasn't Congress simply legislated CO2 regulation instead of this regulatory journey?

Because climate legislation cannot pass the Senate. The Waxman-Markey cap-and-trade bill passed the House in 2009 and died in the Senate. Every subsequent attempt has failed. EPA regulation under the CAA is not Congress's preferred approach; it is the only approach that does not require 60 Senate votes.

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