(a) This subchapter is supplemental to all other provisions of state law governing the issuance of bonds by any governmental unit and, except as otherwise provided in this subchapter, the provisions of state law governing the issuance of bonds by any governmental unit shall continue to apply to the issuance by such governmental unit of taxable bonds.
(b) Nothing herein shall be deemed to broaden or otherwise alter any provisions of state law as they relate to the issuance of the bonds the interest on which is, in some manner, exempt or excludable from federal income taxation.
(c) The reference herein to law providing authority for issuance of bonds shall mean laws now in effect and as hereafter enacted or amended by the General Assembly.
(d) Nothing contained herein shall be construed to impugn the validity of any taxable bonds heretofore issued.