PRESIDENT CARTER'S decision to send nuclear fuel to India is running into solid -- and justified -- opposition on Capitol Hill. India's adamant refusal to accept any international safeguards and inspection of its nuclear facilities, and Prime Minister Gandhi's frequent reassertions of India's right to explode another nuclear bomb if it wishes to, make this export case the ultimate test of the seriousness of U.S. nonproliferation policy.

The central provision of this policy is a requirement of the 1978 law that a country accept full safeguards on its nuclear facilities to be eligible to receive U.S. nuclear exports. With India primarily in mind, the legislators provided a two-year grace period for current customers who did not meet this requirement to give them time to get right with it. Before the grace period expired last March, U.S. negotiators came up with a steady stream of proposals for a mutually face-saving agreement. India rejected them all.

The administration is now using four arguments to support its case. The first is that this proposed export actually does fall within the two-year grace period because India expected the shipments to be made before the deadline expires. This is legalistic gibberish that makes a mockery of the law's clear intent.

The administration also argues that "non-proliferation would be set back by withholding these exports" because they "will help us to maintain a dialogue with India in which we try to narrow our differences." This was the rationale for the several exports that were made during the now-ended negotiations, when there was still some hope -- albeit slight -- that agreement could be reached. It is indisputable that the effects of these exports on non-proliferation everywhere but India will be devastating. All hope of stopping Pakistan's nuclear weapons program and of bringing others such as South Africa and Argentina under the international inspection system is likely to disappear.

A potentially more serious administration argument is that new geopolitical considerations must take precedence over those of non-proliferation. However, despite numerous opportunities to do so, administration spokesmen have been unable to develop this justification beyond the most vague of references to the invasion of Afghanistan. A more specific connection between these two events -- one that also accounts for the recently announced $1.7-billion arms deal between Russia and India -- needs to be drawn before this can begin to be considered a compelling case.

State Department lawyers have also been busy developing arguments in support of India's contention that if the United States fails to approve these exports it will have broken the agreement between the two countries, leaving India legally free to seize and reprocess used U.S. fuel already in that country. In fact, a stronger legal case can be made that India is in violation of the agreement and the fuel contract, which state that India shall "comply with all applicable laws . . . of the United States." Moreover, the agreement between the two nations merely obligates the United States to provide the fuel necessary to keep India's Tarapur reactor "operating continuously." By India's own estimate, U.S.-supplied fuel sufficient to operate the reactor through 1982 is already stockpiled in India.

It is hardly surprising then that Congress appears likely to override the president's decision. The legislattors, at least, seem determined to correct the mistake made in 1974 when the United States failed to make any protest to India's first nuclear explosion -- which relied on illegal use of U.S.-supplied heavy water. The administration seems willing to turn the other cheek. If India explodes a second nuclear weapon, Deputy Secretary of State Christopher told the Senate the other day, why then the United States would certainly stop all nuclear shipments. Sure it would.