the contracts clause was violated by an emergency state statute authorizing extension of the period of redemption from foreclosure sales, for a just and equitable period not exceeding two years, conditioned on payment by the mortgagor of a reasonable rental, as directed by the court.
*516 The mortgage contract was made subject to constitutional power in the Congress to legislate on the subject of bankruptcies. Impliedly, this was written into the contract between petitioner and respondent. "Not only are existing laws read into contracts in order to fix obligations as between parties, but the reservation of essential attributes of sovereign power is also read into contracts as a postulate of the legal order."[20] And the fact that in this case the purchaser at the foreclosure sale was also thewhich the United States, or any agency thereof, or any officer or employee thereof, as such officer or employee, is not a party, the court having jurisdiction of the suit or proceeding shall certify such fact to the Attorney General. In any such case the court shall permit the United States to intervene and become a party for presentation of evidence (if evidence is otherwise receivable in such suit or proceeding) and argument upon the question of the constitutionality of such Act. In any such suit or proceeding the United States shall, subject to the applicable provisions of law, have all the rights of a party and the liabilities of a party as to court costs to the extent necessary for a proper presentation of the facts and