The U.S.-Mexican border is a law made to be broken, a prohibition that breeds gangsters, a long, straight, often virtually invisible line with a curious capacity to twist values, disrupt lives and thwart each stop-gap policy intended to improve its regulation.

Smuggling, a way of life in this area, runs both ways across "the line." Cameras, stereos, calculators, cars and guns -- the "high tech" so highly taxed in Mexico -- is smuggled south. Flesh and blood is brought north.

Narcotics were once a major business here, but that traffic has taken to the air and tended to move east. Along this stretch of the frontier at this moment there is no doubt the smuggler's principal stock in trade is people.

According to U.S. Immigration and Naturalization Service, investigators there are at least 10 major alien-smuggling operations in Tijuana alone. Each is a multimillion-dollar concern.

Some bring aliens from as far away as South America and the Philippines on "package deals" that cost the aliens thousands of dollars apiece. Once the smugglers slip their cargo across the border they transport the illegal immigrants in car trunks, vans, campers or tractor-trailer rigs to a safe house or to destinations in Los Angeles.

An 18-wheeler packed with 40 or 50 or more illegal aliens can be figured by the smugglers to be worth at least $80,000.

"Coyotes," the smugglers are called, or "polleros," which is Spanish for "chicken herder." Often they don't treat their clients as well as most farmers treat their livestock.

But this does not shock people along the border anymore.

At the Sportsman's Den., a bar about 200 yards inside the United States, smugglers can be seen almost any afternoon or evening calling the numbers their "pollos" have given them in the United States and demanding payment.

Rafael Garcia, owner of the bar, simply shrugs. "What can I do?" he says. "It's a public place." But then he adds, "I'm getting tired, very tired of all this."

Even the landscape of San Vaidro and Chula Vista is a map of smuggling. Ravines are known as Smugglers' Canyon and Dead Man's Canyon (after an accidental shoot-out between the border patrol and Mexican undercover police a few years ago). A hill known as the Razorback has been visibly eroded by the thousands of illegal aliens who have crawled, run and slid down its side into the United States.

In addition to the professional smuggling rings, all sorts of amateurs have gotten into the act. U.S. Marines and their wives at nearby Camp Pendleton have been caught smuggling aliens through the base to avoid passing the Border patrol checkpoint at San Clemente. Some marines also went in for beating and robbing the aliens, according to border patrol sources.

Mom and pop tourists are occasionally arrested trying to pay for their vacations south of the border by bringing a few Mexicans north.

But it is typical of the ironic twists life takes along the line that some of the biggest, most organized Tijuana smuggling rings were started by men who once worked undercover for the U.S. Border Patrol.

According to veteran immigration investigators, some Mexicans were hired by the Border Patrol in the early 1950s to act as "gauchos," hooks, to bring illegal aliens across the border then turn them over to the patrol.

It did not take these informers long to discover just how inefficient the Border Patrol could be, and after "Operation Wetback" in 1954, with thousands of Mexicans suddenly forced out of the United States and anxious to return by any means available, the erstwhile gauchos saw there was money to be made in bona fide smuggling.

"They're the bastards that now are giving us hell from one end to the other," said a senior anti-smuggling investigator.

Until recently, undermanned and underequipped, the Immigration Service and its agents in the Border Patrol had barely a prayer of catching the smugglers, and little hope of legal action against them if they did.

Over the last year, however, the investigators finally have been given some tools. The staff of the anti-smuggling unit in Los Angeles has been increased from 6 to 20. A surveillance van has been equipped with video-tape equipment and an electronic "bird-dog" device for tailing cars.

A new law that went into effect a year ago allows the Immigration Service to confiscate vehicles used for transporting illegal aliens. In the first nine months of the confiscation program an estimated $2.3 million worth of vehicles were seized.

Yet here again there is a quirk in the law. Anyone transporting an illegal alien is liable to a felony charge and the confiscation of his car. Theoretically -- and sometimes in practice -- giving a ride to an illegal relative or friend can bring severe penalties. But employing the same illegal alien makes you exempt from punishment.

Both immigration sources and private individuals close to smuggling organizations say, moreover, that the smugglers are cutting their capital losses from vehicle seizures by simply using stolen cars.

Although the number of illegal aliens caught crossing the border has decreased by as much as 20 percent over the last year, few officials believe the decline is the result of deterrence by enforcement efforts. In fact, quite the reverse.

Chief Donald Cameron of the Border Patrol station at Chula Vista attributes the decline to an immigration policy that went into effect April 1 prohibiting raids on homes or places of business. Since fewer illegal aliens are being caught inland, fewer are being shipped back to Mexico to be caught trying to cross a second time.

Other immigration and Border Patrol agents blame the decline on plunging morale in the service.

Twice in the last year Border Patrol agents have been indicted for brutality. In the most recent case three agents, including a supervisor, were charged with assaulting federal officers after striking undercover immigration agents picked up while posing as illegal aliens.

Resentment over such recent charges and investigations within the Border Patrol has made morale worse, but a sense of bitter frustration has become virtually endemic in the service over the last several years.

The agents say they feel they're being overwhelmed, as if the laws they are supposed to enforce are not respected or understood even by the people who make them, much less the people they are trying to catch.

"I got tired of sitting across from a smuggler -- and I hate smugglers -- telling him I'm going to do dire things to him if he's caught and knowing that he knows I'm not going to be able to," said one investigator who recently took early retirement.

"They know they've got us beat just by numbers alone," said senior patrol agent Jim Swartz, 48, as he cruised the border the other night. He was one of about 40 agents deployed on this 66-mile stretch of the line at any given time.

Last year they made 338,561 arrests, more than one third of the total for the entire country. They have no idea of how many got away.

On the entire 2000-mile frontier there are rarely more than 350 agents deployed at a time.

Swartz began to reminisce. "I can remember when we would pick them up and then go over to Tijuana in the evening and have a beer with them. It was like friendly enemies, or, not enemies but they respected us, understood we had a job to do."

"But that's changed now," said Swartz. "Since the early seventies you can feel the hate, sense it."

Other agents say frankly that they are afraid to take the five-minute drive across the border when they go off duty.

On the line, often alone in a patrol car, the agents are the subject of frequent harassment.

"I used to carry a trash can lid myself to use as a shield against rock attacks," said one former line patrolman. "We get them every day. Out there on the line they're really insulting your heritage, you know."

Alberto R. Garcia (no relation to Rafael) says the Border Patrol agents get what they deserve.

Garcia is an immigration consultant in Chula Vista and has been responsible for several investigations of Border Patrol abuses. He has documented several cases.

"I have seen instances of beatings, shootings, deportation of legal residents, deportation of American citizens -- over the years that makes me sick," said Garcia. "They don't have any respect for Mexican people or for Mexican-Americans. They are unhuman. I myself call them Border Patrol outlaws."

The animosity is mutual. The Border Patrol agents make an obscene gesture every time they drive by Garcia's office.