Chuck Norris, America's favorite driftwood sculpture, returns to the screen in "Code of Silence," a conventional cop thriller leavened with a tablespoon of style and a quarter-cup of garbagey fun.

Norris plays Eddie Cusack, a second-generation Chicago detective who plays by his own rules. He doesn't respect the mob's law of omerta , and he doesn't respect the cops' "code of silence," either. When a burned-out bobby given to 90-proof "nerve tonic" shoots an innocent kid, Cusack's the only one who talks.

It takes just such a rugged individualist to stop the street war being waged between Anthony "Crazy Tony" Luna (Mike Genovese) and Luis Comacho (Henry Silva), leader of a band of murderous coke dealers. Luna scotches a Comacho drug deal, stealing both dough and snow and killing Comacho's brother to boot. In search of revenge, the Comacho clan romps around town slitting the throats of its adversaries. This, we are told, is a "Colombian necktie."

The screenplay, by Michael Butler, Dennis Shryack and Mike Gray, is dotted with bits of arcana, fragments of slang drawn from cop culture and the drug underworld that give it a nice texture. These screen writers obviously enjoy what they're doing. They include, for example, a funny skit involving two inept hoods who hold up a tavern full of cops. The script is wildly uneven and often lazy (one line is stolen outright from "The Godfather"). But at its best, it's hard and tough and street-eloquent. When Norris crashes the Comacho pool hall, one hoodlum says, "You don't want to be in here." "If I want your opinion," Norris replies, "I'll beat it out of you."

Director Andy Davis, yet another talented graduate of the Roger Corman School of Cheap Movies, stages the opening sequence with a loose, documentary style that draws the audience directly into the action. His work is uneven, too. A dizzying car chase through the Loop ends in a ho-hum climax, and the final blast-'em-up fails to deliver. But the movie has an unobtrusively daring editing style and use of sound, and a detailed sense of Windy City milieu.

Much of the local texture comes from the supporting cast of fine Chicago actors, including Ralph Foody as the burned-out booze-hound, Joseph Guzaldo as Norris' rookie partner and Dennis Farina as Norris' wounded former partner, who hobbles through "Code of Silence" with retirement schemes ranging from an alligator farm to a hot-dog stand at Wrigley Field. Bert Remsen adds a nice cameo as the commander, as does Ron Dean as a small-minded detective, and Silva is suitably menacing in his high-polish, high-cheekboned way.

Norris has all the charisma of a railroad tie, but he can still karate-kick over his head. His stunts are good, but badly orchestrated. His "tender" moments with Crazy Tony's innocent daughter (Molly Hagan, yet another young performer who acts with her jaw) are simply embarrassing. By this point, though, there's something almost touching about the way Norris keeps butting against the limits of his talent. His obvious inadequacies lend the unbeatable Cusack a touch of the underdog.

The real star of the movie, though, is "Prowler," a four-wheeled riot squad supplied by Robot Defense Systems Inc. of Thornton, Colo. It may unleash fiery mayhem with rockets, recoilless rifles and machine guns aimed by closed-circuit TV cameras, but when it's finished, it mews in a seductive, synthesized woman's voice -- a sort of "My Mother the Tank."

Code of Silence, at area theaters, is rated R and contains considerable violence and profanity.