Like it or not, we're now engaged in a critical debate of the nature, purpose and legal status of marriage.

President Bush has sharply focused this issue by calling for a constitutional amendment upholding marriage as a union between a man and a woman as husband and wife.

How we decide this question - and it will be decided, one way or the other - will shape the future of our society and the course of constitutional government in the United States.

A series of significant judicial decisions have forced this issue upon the nation, beginning with a trial court judge in Hawaii, then a superior court judge in Alaska and then the Vermont Supreme Court. In November, the Massachusetts Supreme Judicial Court declared that traditional marriage upholds persistent prejudices and that same-sex couples have a fundamental right to marry.

Officials in San Francisco have issued thousands of fraudulent marriage licenses to same-sex couples, intentionally violating clear state law, and sued to have a judge declare California's marriage laws discriminatory and unconstitutional.

The effect of these decisions, and intent of the litigation strategy behind them, is unmistakable: to establish same-sex marriage as a civil right that the federal government will then have a constitutional obligation to secure nationwide. Advocates of gay marriage demand, and will accept, nothing less.

In order to reach this outcome, judges disregard thousands of years of custom and experience, flout the laws of every society, and thumb their noses at the beliefs of every major religious tradition. They say that a legal preference for traditional marriage is "irrational."

This question is not about rights but redefining marriage by judicial decree. By circumventing the legislative process, overriding long-standing majority opinion and excluding the people from so fundamental a decision as marriage, these judges threaten our democracy and the rule of law.

In this debate, the guiding principle must be clear: Marriage is a unique institution that is central to the welfare of society - and it must be protected.

Marriage is the formal recognition by society and the laws of society of the most profound relationship that can exist between a man and a woman. By virtue of its function and purpose in society, marriage is a fundamental institution necessary for societal existence and well-being.

But must we amend the Constitution?

As conservatives, we are reluctant to change our most fundamental law. The Constitution should be amended rarely and only for the most important of reasons.

Our constitutional system rightly leaves the power to regulate marriage policy, like so many other things, with the states. Whatever we do, marriage should not become a policy matter for the federal government.

By design, it is difficult to amend the Constitution. Two out of every three members of the House of Representatives and the Senate must approve a proposed amendment - and then it must be accepted by three-quarters of the states.

But this is no mere policy disagreement or matter for social experimentation. Society has never before been confronted with such a concerted legal and political effort to forcefully redefine and thereby undermine one of its most basic institutions. This question can no longer be avoided, and it will not go away.

Despite our reluctance - despite the significance of the endeavor and the awesome task of changing the Constitution - prudence dictates this course of action. The threat to marriage is unambiguous and increasingly imminent. The overriding importance of marriage makes it crucial that we act now.

This is a time for choosing.

If the options are to allow a few activist judges to redefine marriage by judicial fiat, or amend the Constitution to reflect the settled will of the people, the conservative choice is clear.

It is imperative, for the sake of constitutional government, that we proceed with the democratic process of amending the Constitution. It is imperative, for the sake of marriage, that we succeed.

-Matthew Spalding is director of the B. Kenneth Simon Center for American Studies at The Heritage Foundation.