THE FACT that the Cambridge City Council passed a rent control law this September after more than a year of haggling and agitating is no reason to expect an immediate decrease in Cambridge rents. Actually this is just the beginning.

The law that Cambridge has passed is a state law, and every community will be forced to work within its weaknesses and ambiguities. The state legislature passed it last July, in time to boast about it before elections. However, they weren't about to pass anything that would step on too many landlord voter toes.

Any city or town with a population of over 50,000 which ratifies the state law may put its provisions into effect one month after passage and roll back rents to levels of six months before. Under the terms of the law Cambridge rents should have been rolled back to their March 1970 levels as of October 15, but this is not happening. Philip M. Cronin, city solicitor and temporary rent control administrator, has instructed tenants that they are not authorized to pay lower rents until a permanent rent control administrator is appointed. Tenants feel that this is a ridiculous delaying tactic on the part of the city and have filed a suit against Cronin for incomplete administration and failure to comply with the provisions of the law.

At the same time Cambridge landlords are moving to kill the law. The Cambridge Property Owners Association is filing a suit, which will probably be heard in December along with the tenant suit, to get the rent control law declared unconstitutional. They point out that some of the law's provisions, such as the exemption for two-and three-family owner-occupied dwellings, are discriminatory and unconstitutional. They also charge that the term "fair net income" which is used in the law is undefined and unenforceable.

Last month the Property Owners were denied a temporary injunction to halt the law pending a hearing of their suit. At that time Cronin argued for the city in defense of the law stating that the law was constitutional and that it could be put into operation under a temporary administrator. However the law is moving into operation very slowly under Cronin.

In Brookline, the second city in the state to adopt rent control, landlords have succeeded in getting a temporary injunction against the operation of the law pending their suit questioning the law's constitutionality. They brought up exactly the same questions as the Cambridge Property Owners, but the Brookline court handed down a completely opposite ruling. If the suit is successful in getting the law declared unconstitutional, rent control in Massachusetts will be dead for this year.

CRONIN'S overly cautious attitude is perhaps easier to understand in light of this. He has stated that when the law goes into full effect tenants should be able to get rebates for higher rents paid after October first. From his vantage point this probably seems a better solution than letting tenants pay lower rents now, leaving the possibility that landlords could later be able to demand back money if the law is declared unconstitutional.

However there is a clear bias here in favor of the landlords. Cronin and the property owners know that if tenants once start paying lower rents it will be a tricky legal business to get them to pay additional money if the law is declared unconstitutional. To avoid this risk it is much more convenient to keep the tenants paying higher rents for as long as possible. Perhaps the objective is to keep them paying the high rents forever.

This sort of attitude on the part of Cronin and the Cambridge Property Owners Association has pervaded the whole history of rent control in Cambridge. Last year there were two attempts to institute rent control in Cambridge and both of them ultimately were squelched. The first proposal for rent control was brought forward by the Cambridge Housing Authority but defeated by the City Council by a 5-4 vote.

After the defeat of the Housing Authority ordinance the Peace and Freedom Party wrote a similar rent control ordinance and collected the necessary number of signatures to get the rent control question put on the local ballot as a referendum.

However rent control wasn't going to slip onto the books that easily. Cronin gave his opinion that the ordinance was illegal for two reasons. First, an independent expert investigation would have to be made to determine whether or not a housing emergency actually existed in Cambridge, and second, the appropriation of $5000 mentioned in the ordinance was inappropriate because funding is a function that belongs to the city manager.

Partly because of Cronin's conservative legal advice the election commission voted to keep the rent control ordinance off the November '69 ballot.

The Peace and Freedom Party appealed the election commission's ruling but Middlesex Superior Court Judge Henry Leen upheld the ruling in a decision that had a major effect on the future of rent control. Not only did Leen rule out the referendum but he also gave his opinion that no city-instituted rent control program could be put into effect unless the General Court had expressly sanctioned it. He ruled that section 43 of the General Laws specifically gave the power to institute rent control to the General Court and not the individual cities and towns of the Commonwealth. This meant that if Cambridge, or any other city for that matter, wanted rent control it would have to wait until the state did something about it and then accept and work with the state program.

WHEN THE GENERAL COURT finally did pass a rent control law, Cambridge was the first city to adopt it. If Cambridge finally gets to the point of actually administering the law, the Cambridge rent control administrator will be the first in the state to interpret he law's provisions.

One clause that may specifically affect Harvard states that "rental units in any college or school dormitory operated exclusively for charitable or educational purpose" shall be exempt form rent control. The Cambridge rent administrator will have to decide whether or not such housing as Peabody Terrace will fall under this ill-defined category. Cronin has already stated that he interprets the law to mean that such housing would not be covered by rent control.