Rigid clamps placed on secret U.S. intelligence operations by a fearful Congress forced the Central Intelligence Agency to reject a top-priority request for help from Italy in that nation's agony during the abduction and murder of Aldo Moro by left-wing terrorists.

The request was delivered to the CIA by CESIS, a secret liasion arm of Italy's intelligence service. It asked assistance from the CIA in dealing with the menace of the Red Brigades, Christian Democraiic leader Moro's kidnappers and later murderers.

In an earlier era, such a request to be helped by what used to be the Western world's most effective intelligence organization would have been instantly and routinely met. Not so today. Burdened with restrictions impose by Congress and targeted as enemy No. 1 by some of its own former operatives, the CIA was finally compelled to say no to CESIS.

CIA Director Stansfield Turner and his legal advisers wrestled with the request for two weeks before rejecting it. Theoreticaly, they might have ruled the other way, without running afoul of the law.

Their fear, however, went deeper than the cold print of the law. They feared, probably rightly, that even if CIA's clandestine help to Italy in a moment of extreme agony had been ruled technically legal, the chance of discovery by unfriendly congressional sleuths could have fanned it into another political expose. That this was neither subverting a legally elected government nor intruding in another coun.ry's election made no difference.

The law is clear. Signed Dec. 30, 1974, it prohibits all undercover "operations in foreign countries," other than routine intelligence gathering, "unless and until the president finds that each such operation is important to the national security of the United States." Each clandestine operation must be reported to literally dozens of congressmen: members of the Senate Foreign Relations and House International Relations committees, as well as the two intelligence committees.

Despite softening of the anti-CIA mood in Congress fear of political attack that might damage President Carter, Adm. Turner caution in replying to Rome.

An affirmative reply, had it come, would have required days or even week more to a situation where speed was imperative if Moro was to be saved. The 1974 law, written by former senator Harnold Hughes (D-lowa) and Rep-Leo Ryan (D-Calif.), requires a full-fledged meeting of the National Security Council and a specific presidential directive to the CIA before any clandestine operation can be started. Then comes notificaion of the four congressional committees.

The only exception is a "generic" presidential finding that permits clandestine CIA help in dealing with "international" terrorism. The president made that finding months ago. But CIA lawyers, agonizing over Italy's request for help, could not absolutely prove that the Moro-Red Brigades case involved "international" terrorism.

"Sure," one administration official told us, "we know that the Red Brigades are armed with communist-bloc guns, but that isn't easy to prove. Sure we are pretty certain they get training in Eastern Europe, but we don't have absolute proof." Lacking proof of inter-nationalization, the witch-hunt atmosphere that had dominated Capitol Hill's handling of the the CIA the past few years called for extreme caution.

With great reluctance, Turner said no to his Italian couterparts. Instead of gaining access to the CIA's expertise, the Italian government accepted overt assistance froma single State Department psychiatrist, who went t Rome and performed creditably in advising the Italian government on psychological aspects of the case.

These tragic overtones of CIA impotence in a matter of extreme urgency to Italy go far beyond Italy alone. in the past, U.S. intelligence would have been on the scene helping to unlock the secrets of the Red Brigedes, it would also have been the beneficiary of invaluable, on-the-spot information about the Red Brigades and about methods of Italian intelligence.

Exposure to such details is the heart and soul of the intelligence game, permitting the U.S. agents to compite a record that some day could be essential is uncovering future terrorist operations - perhaps in the United States itself. But the CIA's hands were tied in a case demanding speed, courage and political support. The result: costly defeat in the war to preserve democratic institutions.