As soon after August 7, 1961, as may be practicable, the Secretary shall issue regulations specifying standards for approval by him of zoning bylaws for purposes of section
459b–3 of this title. The Secretary may issue amended regulations specifying standards for approval by him of zoning bylaws whenever he shall consider such amended regulations to be desirable due to changed or unforeseen conditions.
All regulations and amended regulations proposed to be issued under authority of the two preceding sentences of this subsection shall be submitted to the Congress and to the towns named in section
459b of this title at least ninety calendar days (which ninety days, however, shall not include days on which either the House of Representatives or the Senate is not in session because of an adjournment of more than three calendar days to a day certain) before they become effective and the Secretary shall, before promulgating any such proposed regulations or amended regulations in final form, take due account of any suggestions for their modification which he may receive during said ninety-day period. All such regulations and amended regulations shall, both in their proposed form and in their final form, be published in the Federal Register.
The Secretary shall approve any zoning bylaw and any amendment to any approved zoning bylaws submitted to him which conforms to the standards contained in the regulations in effect at the time of the adoption by the town of such bylaw or such amendment unless before the time of adoption he has submitted to the Congress and the towns and published in the Federal Register as aforesaid proposed amended regulations with which the bylaw or amendment would not be in conformity, in which case he may withhold his approval pending completion of the review and final publication provided for in this subsection and shall thereafter approve the bylaw or amendment only if it is in conformity with the amended regulations in their final form. Such approval shall not be withdrawn or revoked, nor shall its effect be altered for purposes of section
459b–3 of this title by issuance of any such amended regulations after the date of such approval, so long as such bylaw or such amendment remains in effect as approved.