42 U.S. Code § 7584 - Administration and enforcement as per California standards
Where the numerical clean-fuel vehicle standards applicable under this part to vehicles of not more than 8,500 lbs. GVWR are the same as numerical emission standards applicable in California under the Low-Emission Vehicle and Clean Fuels Regulations of the California Air Resources Board (“CARB”), such standards shall be administered and enforced by the Administrator—
(1) in the same manner and with the same flexibility as the State of California administers and enforces corresponding standards applicable under the Low-Emission Vehicle and Clean Fuels Regulations of the California Air Resources Board (“CARB”); and
(2) subject to the same requirements, and utilizing the same interpretations and policy judgments, as are applicable in the case of such CARB standards, including, but not limited to, requirements regarding certification, production-line testing, and in-use compliance,
unless the Administrator determines (in promulgating the rules establishing the clean fuel vehicle program under this section) that any such administration and enforcement would not meet the criteria for a waiver under section 7543 of this title. Nothing in this section shall apply in the case of standards under section 7585 of this title for heavy-duty vehicles.