The crates of documents the U.S. helped Ferdinand Marcos spirit out of the Philippines contain "smoking gun" evidence of the fallen dictator's crimes against his people. Justice, if not the law, requires that the documents be returned.

That, in a nutshell, is the argument the new Philippine government is making to the Reagan administration -- unsuccessfully, so far.

Severina Rivera, the Washington-based lawyer working to retrieve the documents she says could lead to possibly billions of dollars in "stolen" assets, acknowledges that she doesn't know precisely what documents are in the crates that were taken away on two Air Force planes that accompanied the fleeing Marcos. What she is demanding is her government's right to inspect the documents for evidence of crimes.

Under normal circumstances, such a request from a "friendly government" would have been honored by now, Rivera says. The problem is that the Marcos affair is far from normal.

The major complication is the direct role the United States played in getting Marcos to step down amid deep suspicion that he had stolen not just the recent election but also a staggering amount of money during his 20-year reign. It is not yet known what commitments the Reagan administration made, besides a promise of safe haven, in exchange for Marcos' abdication. That the United States helped him and his wife cart away so much pelf suggests that that might have been part of the deal. If so, the request for access to the documents would put Washington in an embarrassing predicament.

Rivera says that if the only thing involved were personal items and reasonable amounts of cash, the new government would swallow hard and let it go. "But it is too much," she says, "to ask the people of the Philippines to pay a $10 billion bribe to get rid of them."

Nor is she happy with the initial U.S. offer to leave the question of the documents to the courts, which would then hear competing claims to ownership of the documents. "It sounds like neutrality," she says, "but it is a neutrality that favors Marcos." That is so, she says, because her government, not knowing what documents are in the crates, cannot hand the court a list of documents that would link Marcos to specific crimes.

The assumption, though, is that the documents contain important clues to (among other things) the American properties purchased by Ferdinand and Imelda Marcos, presumably with military aid funds from the United States. In addition, the government wants the return of "freshly minted currency that runs into the millions" that was on the Marcos planes.

"We are asking diplomatically for access to copies of the documents so that we can determine what belongs to them and what does not." The idea, says Rivera, is not to impoverish the fallen dictator but merely to retrieve the property he stole.

"The State Department says that six different federal agencies are involved. That may be true. But the fact is the bulk of what he's taken belongs to the Philippine treasury. It is not enough for the United States to say it won't interfere with our efforts to retrieve that property; that favors Marcos. The fact is that the U.S. loaded that stuff in and brought it out, and therefore the U.S. has the responsibility of helping us to recover what belongs to the Philippine people."

The dilemma is this: The U.S. government, when it arranged Marcos's flight, was dealing with a head of state whose continuation in office threatened massive bloodshed. The new government of the Philippines is dealing with a criminal suspect who has left the country with the evidence against him.

That is the still-smoking gun. The Filipinos want it back.