A month has passed since the nephew of Philippine President Ferdinand Marcos and the nephew's bodyguard gunned down a college student and his parents here in broad daylight. No charges have been filed, but that does not surprise many Filipinos.

"What can we do? We're over a barrel," said one official about the case of Marcos nephew, Andres Avelino Barba, 24, whose name has yet to appear in the government-controlled Manila press in connection with the shooting. The student is dead. His parents, still recovering from their wounds, have said little. Government investigators ordered into the case by Marcos have asked few questions, according to witnesses to the shooting.

After six years of martial law, and despite Marcos' promises to clear out improper influences in government, rank continues to have its age-old privileges in the Philippines. The law here often operates as if Manila were a small, ingrown American town, with the press, principal businesses and government all controlled by the same people who manage to softpedal any family unpleasant cries.

Three years ago, when the son of Defense Minister Juan Ponce Enrile and a bodyguard became involved in the shooting death of another youth, the National Bureau of Investigation recommended charges be filed against Enrile's son. None were.The grandson of Foreign Minister Carlos Romulo was charged with rape three years ago in an unusually celebrated case, but court proceedings apparently have been suspended indefinitely.

Americans, as a representatives of the government's principal internationally, are also sometimes included in the power structure and allowed some of its benefits. The mayor of Makati, the heavily commercial district where the Barba shootings took place June 25, said recently that he told his police force several years ago not to file charges against a U.S. ambassador's son who had been arrested in a drug raid. American servicemen facing criminal charges in Philippine courts in the past have been transferred to other countries to escape trial, sometimes resulting in protests here and somethings not.

After the reports of the killing of 17-year-old University of the Philippines student Apolinario Buendia surfaced in the Manila press. Marcos ordered a National Bureau of Investigation inquiry on July 5. But Sulpicio Liberato Sr., a principal witness in the case, said the investigators who visited him asked him no questions about his grabbing and subduing Barba after the young man had allegedly shot Buendia's parents with a 45-caliber pistol. The bureau investigators reportedly have yet to interview the wounded couple. In a telephone interview, the bureau's director said he could not say when the investigation would be completed and made public.

According to eyewitnesses, the shooting arose from an argument during a girl's volleyball game between a team managed by Barba and a neighborhood team in Makati. Barba's bodyguard had begun to argue with some teen-age boys who were distributing the game. One of the guards cleared the court of spectators by firing his M-16 into the air. Then Barba and the bodyguards fanned out into the adjoining streets, looking for the hecklers.

Hearing the commotion in the street, Buendia rushed out of his house, three blocks from the volleyball court, the witnesses say, and he saw two gunmen in the street - one with an M-16 rifle. When he turned his back to return to the house he was shot. A single bullet tore through his intestines and he died the next day.

Rodolfo Buendia, the boy's father, ran and got his own revolver and fired some shots to chase away the gunmen, the accounts continue. The elder Buendia arranged for his wounded son to be taken to the hospital and then went looking for the assailants, who had fled in the direction of the volleyball court. He found them there and a long shootout ensued, which ended when Barba came up behind Buendia and wife, who had tried to restrain her husband. Barba shot them both with his 45-caliber automatic, Liberato, the principal witness, said.

Barba is the son of Marcos' younger sister Fortuna an her husband Marcelino Barba - a colonel in the palace guards. Following the shooting, young Barba an his six bodyguards were taken to police headquarters in Makati, a part of metro Manila, along with three eyewitnesses to the shooting. The bodyguards identified themselves as members of the presidential guards, Marcos' personal battalion.

After statements were taken from the witnesses and from Barba's group, Barba's father, the palace colonel, came to the police station to get his son and the bodyguards. No charges were filed against them. Contacted by phone, the young Barba said, "I have nothing to say," and hung up.

Liberato, who subdued Barba, is a short, stocky man who ekes out a living by running a tiny automotive repair business in his driveway. He pointed out M-16 bullet holes in a neighbor's house and said: "Our people will not feel secure if the members of the president's own family are permitted to run around shooting people."

Earlier this year a military court sentenced a tenant farmer to death for killing his landlord - the son of a politican close to Marcos. The man's neighbors said the peasant killed the politican's son because he and his henchman fired a volley of bullets into the peasant's house in an effort to scare him off his tenancy.