LAST JANUARY, former senator Gaylord Nelson provoked a brief flap among Senate ethics committee members and in the press when he appeared to testify before the Senate energy committee against the nomination of James Watt as secretary of interior. By Sen. Nelson's own account, he was about to join the payrool of the National Wildlife Federation, which opposed Mr. Watt's nomination. The chairman of the ethics committee, Malcolm Wallop (R-Wyo.), at first challenged Sen. Nelson's right to testify, since Senate ethics committee rules prevent ex-senators from lobbying their former colleagues for at least one year after leaving office. Eventually, Sen. Wallop relented, although Mr. Watt survived Sen. Nelson's fusillade to win confirmation.

Situational "ethicists" will be pleased to learn, however, that the tempest over Sen. Nelson's testimony seems to have provoked the ethics committee to reassess its rule on senatorial lobbying, as part of its general review of the Senate's Ethics Code. A UPI story recently quoted the committee's ranking Democrat, Howell Heflin of Alabama, arguing that it would be impossible to enforce the rule unless (and here Sen. Heflin quotes Sen. Wallop himself) "you cut the ears off" their Senate colleagues.

Such drastic moral surgery seems excessive to us, at least at this time; but neither do we endorse Sen. Heflin's and Sen. Wallop's apparent premise: that you can't control senatorial lobbying impulses for a year -- so don't even try. Senate ethics committee members should pause and reflect further before recommending that what surely must now be called the "Nelson Rule" be dropped. There is no necessary rush to revise; the rules committee will receive the ethics committee's recommendations sometime in the spring, before itself offering proposals for changes in the Ethics Code to the full Senate.

At this point, the committee seems ready to junk the "Nelson Rule" altogether rather than try to render some difficult, Solomon-like judgment that divides "approved" senatorial lobbying from other types during the proscribed year. But why not simply allow the rule to stand? It is a minimal but reasonable constraint. Despite the Senate ethics committee's apparent willingness to junk the one-year moratorium rule on lobbying because of a respected former colleague's temporary discomfort, discarding the "Nelson Rule" so lightly really doesn't make sense. "Cutting the ears off" errant senators? Nonsense. Tweaking their ears a bit? Why not?