When the baby sons of Lynne Pilot and Carol Laskin became seriously ill in 1979 because the formula they were fed lacked a vital nutrient, the two Washington-area mothers vowed to prevent future manufacturing slip-ups from causing similar tragedies. Riding a wave of public indignation over the incident, which affected an estimated 20,000 babies fed the formulas Neo-Mull-Soy and Cho-free, they started a consumer group called Formula and propelled a bill regulating the content of infant formula through Congress within a year.

Pilot and Laskin have since learned, to their mounting frustration, that an act of Congress is not always enough to move the federal bureaucracy. Since 1980, they have been battling the Food and Drug Administration and the infant-formula industry over regulations that determine how the law is enforced.

The struggle illustrates two conflicting views of government's ability to make the world safe for consumers. According to the FDA and the industry, the law as currently enforced catches most manufacturing errors, including those that would seriously threaten the health of babies.

The mothers say they will accept nothing less than a guarantee that defective baby formula will never again reach supermarket shelves. Claiming that the FDA has evaded its duty to protect infants, who often receive formula as their only food during the earliest months of life, they have vowed to go back to Congress this year to get the law rewritten with even tighter controls.

Soon after the formula law's passage in 1980, the FDA proposed stringent regulations for its enforcement. But with the change in regulatory climate brought by the Reagan administration, action on the rules stalled within the agency until 1982, when a new scandal, involving almost 3 million cans of two other formulas found to lack vitamin B6, prompted congressional hearings on the delay in enforcement. The hearings provoked hasty publication of a set of final regulations, different from those originally proposed.

Pilot and Laskin were horrified by the final rules, which they say leave too many quality-control decisions up to manufacturers and undermine the intent of the law they fought for. "What we thought we had done was to make sure every batch of formula was tested for every nutrient," Laskin said. Under the present regulations, added Pilot, "it doesn't work that way."

In December 1982, Formula and two other consumer groups filed suit against the FDA in U.S. District Court. In September 1984, the case was dismissed. They appealed the decision last year in the U.S. Court of Appeals for the District of Columbia, and on Dec. 31, 1985, they lost again.

In its decision, the appeals court acknowledged that under the present rules a deficient baby formula could still reach consumers, but advised the groups to take their objections back to Congress and get the law rewritten.

"We have to start all over again," said Laskin. "I have to go get my green corduroy dress out of mothballs," she added, referring to the outfit she wore for most of her Capitol Hill appearances in 1979 and 1980. "Now I think we have to go back and try to strengthen the entire law, and deal with all the questions the court of appeals brought up."

Pilot and Laskin blame themselves for naively accepting advice from congressional staff members during the law's drafting. Laskin said they were persuaded not to insist on the word "batch" because it was a "term of art," and were told that "may" and "must" meant the same thing.

"All the things we argued about six years ago have come back to haunt us," Laskin said.

FDA officials and industry spokesmen say the current regulations are adequately protecting consumers, and that Formula's quest for a guarantee against all possible mishaps is unrealistic.

"You can't write a regulation for infant formula or anything . . . that covers every possible, conceivable situation," said Sanford A. Miller, director of the FDA's Center for Food Safety and Applied Nutrition.

Asked if the current rules would prevent a major outbreak of formula-related illness, as occurred with Neo-Mull-Soy, he said, "I'm afraid to answer that question . . . . Things happen that in 20 quadrillion years you would never believe would happen." But he did predict that the present regulations would prevent such outbreaks if manufacturers obey the rules and consumers inform the FDA if they suspect a problem.

The law passed by Congress in 1980 lists 29 nutrients that must be present at minimum levels in infant formulas. But the final regulations set forth in 1982 allowed manufacturers to choose their own quality-control systems, and exempted six of the 29 nutrients from batch-by-batch testing.

Robert C. Gelardi, executive director of the Infant Formula Council, which represents the major manufacturers, said the regulations have raised the cost of making formula, but are fulfilling their goal. "They're strict regulations and they're working," he said. "In fact, they have caught some problems . . . . "

Miller said that of the eight or nine product recalls since the rules took effect, three were of formulas with too much or too little vitamin A that were caught because of testing required by the regulations. In the other instances, manufacturers released formulas that did not comply with the regulations, and the FDA learned of the products' existence only after they were on the market. "With an agency this size, there's no way for us to know everything that's going on," he said.

Sens. Howard M. Metzenbaum (D-Ohio) and Albert Gore Jr. (D-Tenn.) last year proposed congressional amendments to tighten the formula law's testing requirements, but there has been no action on the bill.

"Looking back now, it the [law] should have been drafted better and tighter," said a congressional staff member who asked not to be identified. "We're not going to get much interest now until the next disaster."

Pilot and Laskin are still energized by their anger over the 1979 Neo-Mull-Soy incident, which left lasting scars on their own families. Pilot's son suffered learning disabilities that now require special education. Dr. Patricia O. Quinn, a developmental pediatrician practicing in the District, said many children fed the defective formulas have specific learning problems that include trouble with word retrieval and abnormalities of balance and coordination.

Pilot said she is determined to prevent another such mistake from harming other children. "I don't think they [formula manufacturers] are bad companies, but there are human beings involved here, and there's human error," she said. "You have to do everything you can to avoid human error, because you're dealing with babies."