Congress made it illegal to publicize knowingly the name of a CIA agent 21 years ago, after it recognized the serious damages the agency could sustain as a result of having its agents exposed.

The 1982 Intelligence Identities Protection Act (search) imposes maximum penalties of 10 years in prison and $50,000 in fines for the unauthorized disclosure of covert agents' identities by government employees with access to classified information.

So far, it has had its desired effect. Government officials cannot recall a time when it had been enforced.

Despite the law's considerable penalties, it does not stop reporters from printing leaked classified information identifying a covert agent.

“There’s a self-censorship that would go on regardless. They understand as well that there’s no legitimate purpose to be served," Ronald Kessler, author of "Inside the CIA," said this week. “There’s no legitimate reason why the press would want to publish these names . . . unless they essentially wanted to work for the other side."

Kessler said that even without the law, the press would not blow the cover of many CIA operatives. But that's not always the case as the public was reminded recently when reports surfaced about the source of a CIA employee's name that appeared this summer in a column by Robert Novak.

The employee, the wife of former Ambassador Charles Wilson, may have been an undercover agent, according to some published reports.

“You have to worry about protecting your sources. When you send a Mrs. Wilson overseas undercover of the State Department, or company X, or some other fiction, you have to try to make that credible,” said former CIA Director Stansfield Turner (search). “If she’s been revealed,” then those she has associated with may be in danger.

Fifteen percent of CIA employees are stationed abroad in 130 countries. The posts range in size from one to 60 employees. A major duty of these agents is to cultivate local informants.

More than 50 CIA officers have been killed. And, in at least one case, the public identification of the agent led to his murder.

In the 1970s, at a time when the CIA was in turmoil, a number of publications, most prominently the Covert Action Information Bulletin (search), published as many as 1,000 CIA agents’ names.

At the center of these exposures was Philip Agee, a former CIA officer. He specialized in anti-CIA literature when he published "Inside the Company: CIA Diary" in 1975 Agee, also a cofounder of the CAIB in which he ran a column titled “Naming Names," turned against the U.S. government and began collaborating with the communists.

Agee was not alone. Counterspy magazine and Who’s Who in the CIA, an East German magazine, also revealed the names of operatives. A Greek publication called Anti revealed the names of 64 Americans it said worked for the CIA, including that of station chief, Richard Welch. The Athens News reprinted his name, address and phone number.

On December 23, 1975, while walking home from a Christmas party, Welch was assassinated.

Not only had the CIA lost a valuable operative, but other agents and informants became more skeptical of the agency’s ability to protect them.

“Beyond the death of a human being it made life more difficult,” Kessler said. “If this started happening on a wholesale basis, it would jeopardize the whole effectiveness [of the CIA]. Anytime a CIA officer is killed that certainly makes some people more hesitant to join.”

Congress passed the Intelligence Identities Protection Act because of Agee's actions. Turner said the law is important because it “puts some teeth into the CIA’s need to protect a few people.”

For a conviction, the disclosure must have been intentional, the accused must have known that the person was a covert agent, and that "the United States is taking affirmative measures to conceal such covert agent's intelligence relationship to the United States."

Though reporters can't be prosecuted, one exception in the law written with CAIB in mind does seek to prevent the distribution of names. Those who engage in a "pattern of activities intended to identify and expose covert agents . . . with reason to believe that such activities would impair or impede the foreign intelligence activities of the United States" can be prosecuted.

Former President George H.W. Bush, the only president in U.S. history who once served as the director of central intelligence, reserved harsh words for those who expose an agent's identity during a 1999 speech.

"Even though I'm a tranquil guy now at this stage of my life, I have nothing but contempt and anger for those who betray the trust by exposing the name of our sources. They are, in my view, the most insidious, of traitors," Bush said.