(a) A State government agency other than the State air pollution control agency may be assigned responsibility for carrying out a portion of a plan if the plan demonstrates to the Administrator's satisfaction that the State governmental agency has the legal authority necessary to carry out the portion of plan.

(b) The State may authorize a local agency to carry out a plan, or portion thereof, within such local agency's jurisdiction if—

(1) The plan demonstrates to the Administrator's satisfaction that the local agency has the legal authority necessary to implement the plan or portion of it; and

(2) This authorization does not relieve the State of responsibility under the Act for carrying out such plan, or portion thereof.