When Exxon Mobil Corp. endorsed a carbon tax proposal initiated by former Secretaries of State James Baker and George Shultz, some observers foresaw a future with dramatically fewer regulations.

Not so, says W. Thaddeus “Thad” Miller, the executive vice president and chief legal officer of Houston-based electrical provider Calpine Corp., who also endorses the Baker proposal. He expects a much less dramatic shift in the regulatory environment if the carbon tax becomes reality.