Brian Brown participates in the US News and World Report Debate Club about the proper role of the federal government in defining marriage:

"...Properly framed, the question raised by the Supreme Court's upcoming constitutional review of California's Proposition 8 and the federal Defense of Marriage Act is whether states and the federal government can legally define marriage as only the union of one man and one woman?

The answer is, clearly, yes.

The United States Constitution says nothing about marriage. The issue of what relationships government recognizes as marriage is a political question, not a constitutional one. States have always been able determine who may legally marry in their states. There are many limitations in the right to marry, including those concerning consanguinity. First cousins are prohibited from marrying in most states, but permitted in others. Some states recognize as valid cousin marriages performed elsewhere, but other states deny them legal recognition. If states have the power to limit marriage to relationships that are not too closely related by blood, surely they have the right to codify the intrinsic male/female nature of marriage.

Similarly, the federal government has the right to define marriage as one man and one woman. Since the purpose of publicly recognizing marriage is to encourage men and women to form stable families to bear and raise children, it is perfectly reasonable for the government to provide benefits and incentives to encourage such family formation. Indeed, encouraging marriage was so important that the federal government even conditioned statehood for Utah on them prohibiting polygamy and adopting laws in line with traditional norms of marriage.