Q: Are price regulations set by the government binding? What about items subsidized by the government?
A: Rules for the benefit of society as a whole that do not negate any Torah law are binding as dina d’malchusa. Therefore, price regulations, if set by the government for this purpose, are binding. Furthermore, the regulations set a commercial standard among the merchants, which is binding on that account (Dinei Mamonos, vol. IV, p. 47).
According to many authorities, price regulations of items subsidized by the government are binding also in Israel, even according the opinion that dina d’malchusa does not generally apply in Israel (Mamon Kasher, p. 89; Pischei Choshen, Onaah 11:).
If the government removed the subsidy from a subsidized item and the price rose, if it imposed rules about the price of products left over from the subsidized period, they are binding. If rules were not imposed and the item is now worth more, the store owner may charge the current price, like any other item that appreciated in value in his possession (Shaarei Ezra, vol. II, C.M. #134).