THE ADMINISTRATION is taking a certain amount of heat for saying it intends to stick within the terms of the 1972 anti-ballistic missile treaty as it continues its work on a missile defense system in space. From the left, it is accused of cynically planning to exploit technicalities and loopholes in the treaty in order to be able to say it is testing within its terms. From the right, it is faulted for failing simply to renounce the treaty, which, its critics maintain, was either flawed from the start or has been effectively trashed by Moscow's violations of it.

These grumbles are predictable: This is an administration that believes that the old arms control agreements undercut American interests and that the Soviets are untrustworthy negotiating partners. On this basis, President Reagan set out to search for a defense that would render obsolete not only nuclear weapons, as he has declared, but also the very need for negotiated arms agreements. Meanwhile, however, Mr. Reagan also entered ambitious negotiations. So he was bound to have to answer to arms control's traditional friends and foes alike.

Traditional arms controllers regard the ABM treaty as the high-water mark in the attempt by the two superpowers to master jointly their nuclear destinies. It helps to recall, however, that the treaty was never regarded as the be-all and end-all of American security. The text provided for research, the sure engine of change, and for amendments, periodic review and even withdrawal. The two powers were serious about the treaty, but they made it warily. They wanted restraints but not a straitjacket.

It is no surprise, then, that there is heavy pressure on the treaty now. It comes from sources well foreseen: technology and distrust. For years the two countries have been conducting research on space defense. They have also accused each other of violations.

The matter of violations is key. The Kremlin can go so much further than any American administration in pressing beyond the terms of treaties: it has no public or opposition to call it to account. This puts a special burden of policing the ABM treaty on Americans. Here it must be said that American conservatives, though they can go too far, have been attentive to issues of Soviet treaty compliance. The Pentagon is right to be troubled by the emergence of a double standard that forces Americans to be faithful to agreements that Soviets compromise. The traditional friends of arms control need to be no less attentive. It could not fail to give the Kremlin extra incentive to satut, for instance, its Krasnoyarsk radar -- a very large and troubling violation -- if the traditional arms controllers took the lead in complaining about it.

Meanwhile, it is better that the Pentagon reshape its testing to stay inside the ABM treaty than that it plan to test outside. Americans who think it's twisting words can go to the political arena, as they are. Soviets who believe the Pentagon is stretching the terms of the ABM treaty can go to the consultative body set up to handle these issues. There they can raise their questions about suspected violations -- and they can also address the many questions about their own enterprises that are on Americans' minds.