The Godfather is an inelegant bar in Northwest Washington, four blocks noth of Tenley Circle, down a flight of dimly lit stairs, where the barroom smells of beer and the entertainment consist of scantily dressed women who -- in the most generous description -- could be said to be dancing.

There, on the night of Nov. 29, Antonio Francisco Azeredo da Silveira Jr., 18, the grandson and adopted son of the Brazilian ambassador, got into an argument over a pack of cigaretts. The bartender told Silveria to leave; there are two versions of what happened next.

The Brazilian Embassy account says that, as Silveira was leaving, he fell, was kicked in the mouth and attacked by five or six people. "Not being able to withstand the agression any longer," the account goes, "he pulled a gun and, though lying down, fired some shots at random."

The police report gives a different version of events: that after Silveira was told to leave, he pulled out two handguns and yelled, "I'm from the Mafia, and I'm going to kill you." One gun misfired, the report says, and Silveira ran outside, chased by two men, one of whom was Kenneth Skeen, 23, a carpenter from Hyattsville, who had begun working as a bouncer at the bar three weeks earlier. Silveira allegedly fired five shots; Skeen was hit three times.

Skeen was hospitalized for eight days with bullet wounds in his hand, leg and stomach. Silveira ended up flying home to Rio de Janeiro. Once he had been identified as the son of a foreign diplomat -- and ther by immune from prosecution under international and U.S. law -- the police had to release him and drop charges of assault with a deadly weapon.

On the Senate floor, Robert Byrd (D-W.Va.) reacted to the incident: "I know nothing about who was in the right and who was in the wrong, but it seems inconceivable to me that a relative of a diplomat can carry a gun in this country and shoot an American and cannot be arrested . . . If this can happen, they can come in, they can burn down our houses if they want to, they can shoot us in the streets, they can mug us, they can rob us, they can rape, they can murder and they cannot be arrested."

Diplomatic immunity doesn't give anyone the right to break laws, but it does protect many diplomats and their families from criminal and civil prosecution.

Not all members of diplomatic missions are immune to civil suits, but those who are can break leases or fail to pay bills without fear of being sued. High-ranking diplomats can be given praking tickets, but they can't be forced to pay them -- and most don't. By law, immunity also is extended to families of some diplomats. Until a government waives that immunity -- which rarely happens -- the most the other government could do would be to order the person out of the country.

The concept is one of the oldest in international law: we'll protect ours. The Babylonians, Hittites and Romans all granted diplomats some form of immunity.

"Without such safeguards it would be virtually impossible to carry out the diplomatic process," says David Newsom, director of the Institute of the Study of Diplomacy at Georgetown University and former U.S. ambassador to Libya, Indonesia and the Philippines. "In some countries it would be easy to trump up charges against a diplomat or his family. That could lead to retaliation and that would get out of hand."

Richard Gookin, associate chief of protocol at the State Department, says that without immunity "it would be extremely difficult to staff our embassies in countries where the rights of individuals are not as respected or as well defined as here."

U.S. diplomats abroad also invoke immunity, although the State Department says it has no statistics on how often. In 1977, Roger Meisner, an American diplomat in Australia, claimed immunity and was called home after a coroner ruled him responsible for a fatal traffic accident. Former ambassador Newsom recalls several cases when someone from an American embassy ran afoul of local law -- a narcotics case, in one instance -- and was sent home rather than face a foreign system of justice. "Usually," he says, "it's handled quietly."

In Washington, 21,218 members of diplomatic missions are immune from criminal prosecution. Only 10 of them got in trouble with District police last year, according to a police tally. There were three cases of alleged drunk driving and three cases allegedly involving illegal weapons.

In each case, the police sent a report to Gookin's office, and he reviewed the matter with the embassy involved to "express our concern." Neither he nor the police will disclose details of those incidents or what action the State Department suggested. "We prefer to handle it confidentially," Gookin says. "We try to avoid embarrassing any foreign mission."

But occasionally someone with diplomatic immunity attracts notice. In 1959, a car driven by the 21-year-old son of the Irish ambassador struck and killed Jossie Hamlin, a cleaning woman, as she was crossing a Washington street. The youth was arrested and charged with homicide, but the charges was dismissed and the youth was sent home.

In 1974, police reported that a car driven by an attache at the Panamian Embassy ran a red light and collided with a car in which Dr. Halla Brown, a professor at George Washington University Medical School, was a passenger. Brown was paralyzed for life. The attache, uninsured, couldn't be compelled to pay damages. Some congressmen threatened to cut off aid to Panama, and eventually its government paid $100,000 toward Brown's medical expenses.

In 1979, the son of a diplomat from Gabon was accused by Mongtomery County authorities of setting fires that caused $31,000 damage to a county junior high school. The boy was expelled from school but was not charged with arson. After the State department presented the allegations, Gabon ordered the boy and his family home.

In 1978, Congress revised the law on diplomat immunity. In keeping with the practices of most other countries, it limited immunity and required diplomats to carry automobile insurance. The old law, unchanged since 1790, gave everyone from the ambassador to the ambassador's valet immunity from criminal charges and civil suits.

Under the new law, only the higher-ranking diplomats and their families -- 10,098 persons in Washington at last count -- retained full immunity. The embassies' support staffs --3,177 workers -- retained civil immunity only while they wer on official business. The staffs' families -- another 7,943 persons -- lost all civil immunity. And 300 servants lost all immunity.

William Hathaway, then a senator from Maine, wanted to go farther and proposed that the State Department compensate Americans injured by or who had valid claims against persons protected by diplomatic immunity. Hathaway said the government and U.S. diplomats abroad -- not the average citizen -- reap the prime benefits of diplomatic immunity. The burden of diplomatic immunity, he argued, "should not be borne by people who are really just innocent third parties."

The State Department successfully opposed the proposal, contending, as Gookin told Congress, that it would encourage "diplomats and their governments not to assume their responsibilities in the expected manner."

An American who gets into a dispute with someone who invokes diplomatic immunity has limited options. In a traffic accident, an American can sue the diplomat's insurance company. But if the insurance doesn't cover the damage -- in Washington, the mandatory liability is only $10,000 per bodily injury and $20,000 per accident -- the injured motorist can't sue the driver for the rest.

Gookin says the State Department will "use our good offices" to settle disputes between an American and someone with diplomatic immunity. In 1982 the State Department received 82 complaints abut unpaid bills and 22 about lease problems; 48 were resolved. The rest are pending.

The case of Kenneth Skeen, the bouncer shot at The Godfather, may not be resolved for awhile. Skeen's lawyer, John Coale, filed a $10 million suit against the government of Brazil under the Foreign Sovereign Immunities Act of 1976, which allows American citizens to sue foreign governments for acts committed by an official or employe of that government "while acting within the scope of his office or employment."

State Department and Brazilian officials won't comment on the lawsuit. Seven weeks after the shooting, Skeen was back to work as a carpenter but says he hasn't regained his strength. He says he's confused and angry "that our government let that kid go just because his father is an ambassador . . . What if I had died? Would they still have set him free?"

At the State Department, Gookin says, "In the event of a death, we could ask for a waiver of immunity so the accused could stand trial. But if the other government turned that request down, we'd have to live up to our international obligations and someone with immunity would have to be released . . . Then, no, it wouldn't have made any difference."