THREE YEARS ago, Congress ended a longstanding stalemate and passed what was supposed to be a tough new law regulating pesticide residues in the food supply. The action was partly in response to a court case which raised the possibility that without legislation, a fragment of prior law would be used to ban some major pesticides. Industry groups that previously had blocked the bill suddenly found it in their interest to compromise.

Most pesticides in use were licensed long ago. The new law set up a strict timetable for reconsidering their safety according to modern standards; required that they be judged not by their effect on the population as a whole but by the possible effect on children, who are more vulnerable; and required that the Environmental Protection Agency take into account the cumulative effect of all pesticides rather than judging each in isolation. The president hailed it as "the peace of mind act because it will give parents the peace of mind that comes from knowing that the fruits, the vegetables, the grains . . . their children [eat] are safe."

Now, however, the first major deadline under the act has passed, and a group of environmental and other organizations has sued the administration for failure to enforce the law. The agency over the years has issued about 9,000 tolerances -- rules governing how much of a given pesticide can remain on a given product when it goes to market. It was supposed to review a third of those in the first three years of the act, the riskiest pesticides first. The lawsuit says that instead it met the quota by revoking more than 1,000 "paper" tolerances governing pesticides no longer in use or applications that no longer occur.

It promised to complete the review of an entire class of dangerous pesticides -- organophosphates -- by the third anniversary but hasn't, though it did ban the use of the worst one on foodstuffs beginning next year and limited the use of one other. The suing parties, led by the Natural Resources Defense Council, question whether, in part, the administration has yielded to continuing pressure from industry and farm groups to "relax protections."

The administration says not so, that it has met as many of the requirements of the law as practicable, that as ever on issues such as this the science is hard, that particular problems occur in measuring effects on children and cumulative exposure, that it's better in the long run to do the thing right than fast, etc. Politics may be mildly at work as well.

The vice president, whose office has had a hand in the implementation of the law, has a current interest in looking measured on environmental issues such as this. It may not be a propitious time to lay an added regulatory burden on already hurting farmers, either. EPA is also chronically torn on the issue. In this as in all administrations, it spends part of its time assuring the public that it will rid the food supply of dangerous chemicals, the rest assuring the public the food supply is safe.

But pesticide regulation has been on the books for years. Not much has happened. Enough evidence of possible harm exists that at least some scientists are worried, particularly as to the cumulative effects on children to which this legislation speaks. The agency has done a less than vigorous job of enforcing the pesticide law in the past. It bears an extra burden when it now asks for time because the job is undeniably hard.