It's as if Secretary of Defense Donald Rumsfeld has hung out a sign at the Pentagon: From now on, U.S. missile-defense policy will be made in accordance with how things are, not with how they used to be.

That's the upshot, anyway, of what the secretary said at a recent press conference. Rumsfeld pointed out that the national security environment that produced the 1972 Anti-Ballistic Missile (ABM) Treaty, which we signed with the Soviets, no longer exists. Neither, for that matter, does the Soviet Union. In view of this, he said, it's time for the United States to get to work building a global missile-defense shield.

Rumsfeld continued this display of U.S. resolve during a subsequent trip to Europe, where he told numerous security leaders-many of whom are hostile to the concept-to face the fact that a shield will be built.

Gone not only are the times that produced the treaty, and the adversary that made it necessary, but the relationship the treaty addressed. The United States signed the ABM Treaty-which barred deployment of a missile defense system and imposed severe restrictions on development and testing-in an attempt to slow down the arms race and stabilize its relationship with the Soviet Union.

Reasonable people can disagree over whether it was the correct strategy at the time. But why do arms-control advocates still cling to the ABM Treaty as "the cornerstone of strategic stability," a phrase heard often on both sides of the Atlantic? The primary threat to the United States comes no longer from a calculated strategic nuclear attack by the Soviet Union but from accidental or unauthorized missile attacks by established powers or from calculated strikes by rogue states such as Iran, Iraq and North Korea.

The Russians charge that an American missile defense will spark a new arms race. They claim to have weapons capable of penetrating such a defense. President Bush could quiet Russian protests-and sever Russian interests from those of the Chinese, who also vehemently protest a U.S. missile defense-by taking a cue from President Reagan and his father, who offered to let the Russians join us behind any missile shield. And the Chinese can't reasonably expect to dissuade America from constructing such a defense while they sell weapons to the very states that pose the most significant threats to American security.

Those who think we should retain the ABM Treaty assume the same agreement that stabilized relations with the old Soviet regime somehow will protect us from the fundamentally different dangers now facing the United States. In a recent issue of "Inside Missile Defense," Spurgeon Keeny, president of the Washington-based Arms Control Association, wrote that to walk away from the treaty would represent an abandonment of the security approach "that has been painstakingly fashioned on a bipartisan basis over the past three decades."

This is fantasy. We're essentially being asked to believe that-by a magical coincidence-a Cold War instrument is perfectly suited to addressing current threats. President Bush and Secretary Rumsfeld simply have recognized the pointlessness of using the old approach to solve new problems.

This recognition has taken hold even among those who helped craft the treaty, such as former Secretary of State Henry Kissinger. He told the Senate Foreign Relations Committee in May 1999 that it is strategically and morally necessary to build a missile defense, given current security threats. The United States needs to "find a way to end the restrictions the ABM Treaty imposes on the research, development, testing and deployment of missile defense systems as soon as possible," he said.

Secretary Rumsfeld's comments, which clearly echo those of Secretary Kissinger, recognize that yesterday's Cold War instruments cannot solve tomorrow's security problems. The Cold War ended a decade ago. It is past time the United States gets on with the business of building a missile defense system to protect the American people.

If not? Kissinger probably put it best. "I cannot imagine what an American president would say to the American public if there should be an attack and if he would have to explain that he did nothing to prevent or defeat the resulting catastrophe," he told the Senate committee. "The legitimacy of government would be threatened if such a condition existed."

It apparently won't-now that we've signaled our willingness to shed the ABM straitjacket.

Baker Spring is a research fellow in the Davis Institute for International Studies at The Heritage Foundation