Late last week, Senate and House Democrats piled more pressure on EPA’s efforts to regulate greenhouse gases under existing Clean Air Act authority. Senator Rockefeller and Representatives Rahall, Boucher, and Mohollan introduced companion House and Senate bills to preclude EPA regulation of stationary source GHG emissions for two years. Unlike the resolution sponsored by Senator Murkowski, which would simply overturn the endangerment finding and thus preclude all GHG regulation, the new legislation would specifically allow mobile source regulation to proceed.

As long as the White House and important committee chairs oppose the legislation, it still seems unlikely to pass, though there have been enough political surprises in the past few months, and there are enough moderate Democrats supporting some kind of preclusion of EPA regulation, that I would no longer rule it out.

Even if the bills are not enacted, the filing of the legislation remains noteworthy. First, Representative Boucher was one of the early, and perhaps most surprising, supporters of cap-and-trade legislation. At a policy level, support for legislation and opposition to EPA regulation under existing authority is perfectly reasonable. I should hope so, because it’s a view that I share. Nonetheless, it still strikes me as a telling example of how much momentum seems to be building to slow down the more aggressive aspects of EPA’s approach to GHG regulation.

The flip side of this coin is EPA’s announcement that it will not require permits for GHG emissions until 2011 and that the program will initially cover only sources emitting at least 75,000 tpy of GHG. Time will tell whether administration opposition and EPA’s moves to limit the pain of stationary source GHG regulation will be enough to beat back the opponents of any GHG regulation under existing authority.