Answer:
The Clean Air Act of 1970 is one of the first American environmental laws. It is also the first major environmental law that authorizes citizens to follow the interest to act of private persons against associations, companies or the State when these do not respect the law. These regulations, the application of which depends on the Environmental Protection Agency, were greatly relaxed during the presidency of George H. W. Bush.
If the EPA is responsible for the regulatory application of the CAA, it can leave the States the right to take care of it, and is even encouraged to do so in order to take into account local specificities, provided that these submit a State Implementation Plan. States can nevertheless refuse to take charge of the application and compel the EPA to do so.