The Senate's lingering dispute with the Reagan administration over the art of treaty ratification reminds you of Sam Ervin's question: ''What's the Constitution among friends?''

Ervin's question satirized the familiar tendency, which knows no party or cause, to seek constitutional shortcuts that suit the moment, never mind the implications. Which is precisely what the administration has been doing about the 1972 antiballistic missile (ABM) treaty.

The treaty was long considered to bar certain kinds of ''exotic'' testing now deemed essential to ''Star Wars.'' So the administration conveniently began to contend, several years ago, that the traditional understanding of the treaty (based on what Nixon administration officials had told the Senate in 1972) was disputable. The ''real'' meaning of the treaty, a very different one, would emerge from an inspection of the ''negotiating record,'' a heap of old documents.

Sen. Sam Nunn, who with Senate Majority Leader Robert Byrd is seeking a clarification, spotted the problem immediately. So did others. It wasn't hard to see that the new view of ratification challenged the Senate's role fundamentally.

For if senators couldn't rely on what the executive branch said a treaty meant -- if instead they must sift through a voluminous and perhaps baffling ''negotiating record'' -- the process of agreeing to ratification would be much complicated and prolonged.

More to the present point, the INF treaty, whose approval is now so eagerly sought, could be stalled in the Senate for months.

Since Nunn and Byrd wrote to Secretary of State Shultz the other day insisting on a clarification, these Senate concerns have been derided. An unidentified White House official pronounced the worries ''curious.''

What the derision shows, unfortunately, is the brevity of Republican historical memories. For it wasn't the Democrats who first challenged the executive erosion of the Senate's treaty-making authority.

Doesn't anyone remember the Bricker Amendment? That proposal, sponsored in 1952 by Sen. John Bricker of Ohio, reflected an angry perception that presidents were abusing the treaty-making power -- in that instance to do what ordinary ''domestic'' legislation couldn't do. Under a famous Supreme Court precedent, an executive agreement between the United States and Canada overriding state laws on migratory game birds had been allowed to stand.

Bricker charged that the treaty-making power (augmented by ''executive agreements'') had become a favored instrument of executive aggrandizement at the expense of Congress and the Constitution. His amendment would have required a congressional act of enablement with every treaty.

It was a bad idea, excessively restrictive of presidential authority. But there was a certain flinty integrity in the old-fashioned GOP constitutional fundamentalism it reflected. For it is, after all, indisputable that the framers had intended the Senate to be the primary treaty-making branch of U.S. government. The usurpation and exploitation of that function by presidents outraged Republicans of the Ohio school.

The attack on the Senate's treaty-making authority is different now. Still, one wonders what a Bricker or a Robert A. Taft would have to say about the view of treaty ratification advanced by the Reagan administration.

That view implies that when a treaty is negotiated and presented for Senate agreement, senators must play a guessing game about what it means. If they guess wrong, they expose themselves to surprises -- to the possibility of being told sometime in the future: ''You might have believed what you were told by the Reagan administration in 1988, but this is 2000 and this is not the Reagan administration and the joke's on you. You should have taken a closer look at the negotiating record, all 10,000 pages of it.''

That is why Nunn and Byrd are insisting that the administration decide, and declare, how seriously the Senate may take its testimony about the meaning of treaties, beginning with INF. They should settle for no less.