Not the least stimulating aspect of Oliver North's six-day stand was his emergence as a constitutional philosopher, beating the drums for a one-man presidential band in foreign policy. And when the colonel paused for supporting evidence, he twice cited the famous 1936 Supreme Court case U.S. v. Curtiss-Wright Export Corp.

The case is indeed central to any dispute over congressional-presidential balance in the making of foreign policy. But the colonel turned it upside down.

Sen. George Mitchell of Maine, a former judge, happened to have the floor when North first mentioned the case. Mitchell contested North's interpretation, and the usually confident colonel scurried for cover, pleading the one-sidedness of any constitutional joust between a former judge and a colonel of infantry.

Yet the following day, North returned to the Curtiss-Wright case. And this time he got away with suggesting that the Supreme Court had endorsed foreign-policy soloing by the president and his aides. No one said him nay.

North's general theory, it seems, is that Congress' principal responsibility in foreign-policy matters is to stay out of sensitive or secret executive operations. All a president need do is dub his enterprises with the talismanic label ''covert operation.'' Congress is then obliged to stay out of his hair.

To crown this sweeping view, North even added that it is entirely constitutional for a president, when denied regular funding, to turn (as North and others did in Reagan's behalf) to private angels and persist, privately if necessary, in the face of congressional displeasure.

North cheerfully conceded that this is the constitutionalism of a mere infantry colonel. But since none of his interrogators challenged him, North's admiring audience might well have assumed that his doctrine of presidential power is gospel. North, after all, is hardly the first or only advocate of a view of presidential authority that would do credit to the most daring counselors of Charles I -- the ill-fated monarch who attempted to raise revenues without convening Parliament.

However, in choosing the Curtiss-Wright case as the central buttress of his theory, North tumbled into a self-set trap. The issue in that case was, ironically, a power delegated by Congress -- the authority to embargo arms shipments to two warring South American nations. When President Roosevelt proclaimed the embargo and Curtiss-Wright fell afoul of it, the company complained of an illegitimate delegation of power. The challenge was rebuffed, and the court made some interesting collateral comments on presidential power. But no one so much as suggested that the power at issue was anything other than Congress' to delegate.

The court, as North noted, quoted George Washington to the effect that the president is the nation's ''sole organ'' in foreign policy. But by long and accepted construction, this means only that in foreign policy the nation for many practical reasons speaks with one voice. It is far from the same as claiming that presidents alone are empowered to make foreign policy.

As Justice Robert Jackson said in the Steel Seizure case of Korean War days: ''When the President takes measures incompatible with the expressed or implied will of Congress, his power is at its lowest ebb. . . . For what is at stake is the equilibrium established by our constitutional system.'' This doctrine bears directly on the current dispute over the degree to which the administration might be bound by the Boland Amendments.

The North doctrine of presidential power acknowledges no such ''equilibrium,'' only a president who in foreign policy calls the shots solo. That view is not only contrary to the Curtiss-Wright ruling, it ignores most of the long, tangled history of presidential-congressional rivalry. Presidents aren't messenger boys, but they aren't independent agents either.

Sen. Mitchell or someone should have asked North whether he'd ever read Article 2 of the Constitution and if so, where in its text he finds the sweeping grant of authority he thinks is there.

Someone also should have reminded the colonel of the near-absolute principle that the power of the purse belongs to Congress. If a president or his aides need only shake down a few eccentric millionaires to fund any foreign-policy enterprise they fancy, anywhere in the world, there is no reliable limit on the foreign entanglements into which the nation might unwillingly and unwittingly be dragged.

That is a point these hearings should make over and over, if they make no other.