Judge Paul C. Reardon of the Massachusetts Supreme Court yesterday declared the state's five-month-old rent control law-now in effect in Cambridge and Brookline-to be constitutional.

The court's unanimous opinion also validated procedures used by the Cambridge Rent Control administration-which include requiring landlords to disclose detailed information about their property-saying they were necessary to enforce the controls.

However, the court dismissed a suit brought by several Cambridge tenants, who charged temporary rent control administrator Philip M. Cronin '53 with falling to enforce the provisions of the law, as having no legal basis. After the Cambridge City Council passed the law in September, Cronin issued an order temporarily adjusting Cambridge rents to the current level rather than the March 1970 rollback level outlined in the law.

Fair Profit

Last week Cronin issued a statement which set the fair profit rate for a landlord at between 10 and 15 per cent of the market value of the property. Tenant groups throughout Cambridge have attacked this standard as one which will again cause rents to spiral. The Cambridge City Council has called for a hearing on the matter at 8 p. m. tonight.