Upon the effective date of regulations under this subchapter no State or political subdivision may impose any requirements less stringent than those authorized under this subchapter respecting the same matter as governed by such regulations, except that if application of a regulation with respect to any matter under this subchapter is postponed or enjoined by the action of any court, no State or political subdivision shall be prohibited from acting with respect to the same aspect of such matter until such time as such regulation takes effect. Nothing in this chapter shall be construed to prohibit any State or political subdivision thereof from imposing any requirements, including those for site selection, which are more stringent than those imposed by such regulations. Nothing in this chapter (or in any regulation adopted under this chapter) shall be construed to prohibit any State from requiring that the State be provided with a copy of each manifest used in connection with hazardous waste which is generated within that State or transported to a treatment, storage, or disposal facility within that State.