Section 12. Upon petition in writing, with an affidavit that it is signed by not less than twenty-five per cent of the Massachusetts producers who, during the month of April in the license year next preceding that in which such petition is filed, produced and delivered milk for sale or distribution as fluid milk in any particular market the boundaries and limits of which shall be set forth in said petition, and which said petition alleges that the price to the producer established under authority of this chapter or by any agreement, license, regulation or order made or issued pursuant to any federal law cannot otherwise be maintained, and further alleging that the maintenance of such price is necessary in order to secure a regular, continuous and adequate supply of fresh, pure milk sufficient to meet the requirements of the market named in said petition and to protect the public health therein, and which petition requests the commissioner to establish minimum prices, wholesale or retail, or both, for milk for such market, and if after making such examination and investigation as is authorized by this chapter or is necessary to ascertain the facts, and after public hearing held after due notice, the commissioner finds at the close of such hearing and investigation that such petition is signed by not less than twenty-five per cent of such producers who, during said month or such subsequent month as the commissioner may find is a more representative period, produced and delivered milk for sale or distribution as fluid milk in said market, that the price to the producer established under authority of this chapter or by any agreement, license, regulation or order made or issued pursuant to any federal law, cannot otherwise be maintained, and that the maintenance of such price is necessary in order to insure a regular, continuous and adequate supply of fresh, pure milk sufficient to meet the requirements of said market and to protect the public health therein, the commissioner may declare that a state of emergency exists. The commissioner is thereupon authorized to issue such orders, rules and regulations as may be necessary, including the fixing by official order of minimum wholesale or retail prices, or both, for milk sold within the market affected, irrespective of where such milk is produced. The commissioner may in like manner at any time alter, revise, amend or rescind the prices so fixed. Any such action taken by the commissioner shall be reviewed by the commissioner at least once in each year thereafter, and, if not thus reviewed, the orders issued shall terminate upon the expiration of the period of one year after the date of the issuance of such orders, and any action may likewise at any time be thus reviewed on the order of the governor. Due notice shall be given of any such review. Any price fixed pursuant to this section, and any alteration, revision or amendment thereof shall be fair, just and reasonable and shall be published as provided in section nineteen.