Clean Air Protection Act - Makes the United States Supreme Court's decision in Massachusetts v. Environmental Protection Agency and any establishment of standards resulting from the proposed rule published by the Administrator of the Environmental Protection Agency (EPA) entitled "Proposed Endangerment and Cause or Contribute Findings for Greenhouse Gases Under Section 202(a) of the Clean Air Act," or any similar or subsequent rule or other action relying on that decision, applicable only to sources regulated as of the date of enactment of this Act under such section (which concerns emission standards for new motor vehicles or new motor vehicle engines).