THE "GOLDEN FLEECE" award didn't sound like such a bad idea when Sen. William Proxmire cranked it up five years ago.The award -- a kind of booby prize -- was to be used to publicize wasteful government spending. The goal -- to shame government officials into shaping up -- was reasonable, and the name of the award guaranteed the publicity necessary to do that. But somewhere along the line, the thing has gone geflooey. The award has boomeranged on Sen. Proxmire and the other members of Congress -- not to mention on the taxpayers.

It happened like this; the second award, five years ago, went to three government agencies for supporting a Michigan professor's research into the aggressive behavior of monkeys. In a speech on the Senate floor, a press release and a newsletter, as well as during subsequent public appearances, Sen. Proxmire ridiculed the project, claiming it was worthless and a rip-off of the taxpayers. The professor, not surprisingly, sued for libel. The other day the case was settled when Sen. Proxmire agreed to pay $10,000 out of his own bank account to the professor.

If that were all, it would be an unexceptionable result. A victim of the Golden Fleece attack was entitled to defend himself. And, anyway, too many of these awards have provided examples of the senator's inability to comprehend the usefulness of some research rather than examples of wasteful government spending.

But other issues were involved here. The taxpayers got stuck with Sen. Proxmire's legal bills -- $124,351 worth -- because the Congress saw the suit as a defense of its own treasured immunity from libel charges. The case had threatened to strip away much of that immunity. The question was this: was Sen. Proxmire's charges protected by senatorial immunity wherever he made it?

Last summer, the Supreme Court ruled that Sen. Proxmire could not be held liable for what he had said in his speech on the Senate floor -- that was a part of his legislative duties, which, under the Constitution, could not be questioned elsewhere. But the court said that this immunity did not extend to press releases, newsletters, speeches made elsewhere and telephone calls, since these were not part of his legislative duties.

That decision strikes us as having been too sweeping. A senator's job doesn't end when he walks off the floor or out of a committee meeting, despite the court's conclusion that it does. But there is something to the lines the court has drawn. It means members of Congress can't go around saying anything they feel like about ordinary citizens without having to account for it, occasionally, in court. If that makes them do their homework a little more carefully, nothing but extravagant and libelous boilerplate will have been lost. And if it eliminates the Golden Fleece awards, well -- we think the country could live with that.