The Supreme Court yesterday gave the Central Intelligence Agency absolute power to keep its sources of information secret, even if the sources are not confidential and the information itself is not classified.

In a 7-to-2 decision written by Chief Justice Warren E. Burger, the court said Congress in 1947 gave the director of central intelligence "very broad authority to protect all sources of intelligence information from disclosure."

The decision overturned a ruling by the federal appeals court here that the CIA said would cripple its ability to gather intelligence because the agency would be forced to reveal sources and its researchers in controversial experiments involving mind-altering drugs.

The "forced disclosure of the identities of its intelligence sources could well have a devastating impact on the agency's ability to carry out its mission," Burger said yesterday in an opinion that showed the court's willingness to defer to arguments raising national-security issues.

Justice Thurgood Marshall, joined by Justice William J. Brennan Jr., agreed that the appeals court erred in ordering the material released. But Marshall said the majority went too far to protect the agency not only from revealing sources but also from revealing what types of information it wanted to collect.

"Even newspapers and public libraries, road maps and telephone books appear to fall within the definition adopted by the court today," Marshall said.

The ruling directly applies to the CIA. But the reasoning might also apply to all agencies engaged in foreign intelligence -- including the National Security Agency, the Defense Intelligence Agency, the National Reconnaissance Office, the FBI's counterintelligence branch and intelligence units of the State Department and other agencies.

The case involves a 1977 Freedom of Information Act lawsuit against the CIA by attorney John C. Sims and Sidney Wolfe, director of Public Citizen Health Research Group.

Sims and Wolfe sought the names of individuals and institutions that had performed research under the CIA's MK/ULTRA project, which was financed from 1953 to 1966 and established to counter Soviet and Chinese brainwashing techniques.

It included the drug experiments, in which researchers administered LSD and other dangerous drugs to unwitting persons. At least two persons died as a result of the experiments, and others may have been seriously injured.

The agency refused to reveal the researchers' names or many of the institutions involved, citing the 1947 law saying the CIA director is required to "protect intelligence sources and methods."

Sims and Wolfe argued that the agency could not claim that releasing the information could damage the United States because the information was not classified and because many of the researchers and institutions were not promised confidentiality and did not even know that the CIA was sponsoring the research.

A federal appeals court ordered much of the information released, defining "intelligence sources" as only those to which the CIA had to guarantee confidentiality in order to obtain the information.

"The court of appeals underestimated the importance of providing intelligence sources with an assurance of confidentiality that is as absolute as possible," Burger said yesterday.

Under the appeals court's approach, he said, the agency "would be forced to disclose a source whenever a court determines, after the fact, that the agency could have obtained the . . . information supplied without promising confidentiality."

"We seriously doubt whether a potential intelligence source will rest assured knowing that judges, who have little or no background in the delicate business of intelligence gathering, will order his identity revealed only after examining the facts of the case to determine whether the agency actually needed to promise confidentiality in order to obtain the information," Burger said.

Disclosure of the agency's research, he added, "may compromise the agency's ability to gather intelligence as much as disclosure of the identities of intelligence sources. A foreign government can learn a good deal about the agency's activities by knowing the public sources of information that interest the agency."

The CIA, in a prepared statement, said yesterday's decision in the case, Central Intelligence Agency v. Sims, would "send a powerful message to current and prospective intelligence sources that the agency can, indeed, fulfill their expectations of confidentiality."

Paul Alan Levy, an attorney for Sims and Wolfe, called the ruling a "severe setback for the public's right to learn about abuses by national security agencies and for the principle that decisions of those agencies are subject to judicial review."

The agency, he said, would be able to withhold information "even if it does not or cannot show disclosure would be harmful to the national security."