Pub. L. 91-173, tit. V, sec. 506
effect on state laws
effect on state laws Sec. 506. (a) No State law in effect on the date of enactment of this Act or which may become effective thereafter shall be superseded by any provision of this Act or order issued or any mandatory health or safety standard, except insofar as such State law is in conflict with this Act or with any order issued or any mandatory health or safety standard. (b) The provisions of any State law or regulation in effect upon the operative date of this Act, or which may become effective thereafter, which provide for more stringent health and safety standards applicable to coal mines than do the provisions of this Act or any order issued or any mandatory health or safety standard shall not thereby be construed or held to be in conflict with this Act. The provisions of any State law or regulation in effect on the elate of enactment of this Act, or which may become effective thereafter, which provide for health and safety standards applicable to coal mines for which no provision is contained in this Act or in any order issued or any mandatory health or safety standard, shall not beheld to be in conflict with this Act.