Nothing in this chapter shall be construed to prohibit a State from enacting and enforcing a standard or requirement that is identical to a standard or requirement established or promulgated under this chapter. Except as provided in sections 14322(e) and 14323 of this title, nothing in this chapter shall be construed to prohibit a State from enacting and enforcing a standard or requirement that is more stringent than a standard or requirement established or promulgated under this chapter.