The government’s real interest in wedded bliss tends to be obscured in the debate attending the Supreme Court’s pending rulings in two marriage cases. Sorry to disappoint, but the state isn’t interested in the love lives of citizens just for the sake of romance.

No, government has an interest in marriage because the act that unites a man and a woman creates new life. And this new life needs and deserves a mother and a father—because otherwise, the social costs run high.

At stake in the two cases expected to be decided by the Supreme Court later this month is whether citizens and their elected officials have the constitutional authority to make laws that reflect the truth about marriage.

One case concerns the federal Defense of Marriage Act (DOMA), which defines marriage for the purposes of federal law. Passed by overwhelming majorities in both houses of Congress in 1996, DOMA was signed into law by President Bill Clinton. Congress passed DOMA to make explicitly clear what was known at the time of our country’s founding—that marriage is the union of one man and one woman.

Some have argued that Congress lacks authority to make marriage policy for federal purposes and that it has to accept whatever definition of marriage the states come up with. For this reason, they conclude, the Supreme Court should strike DOMA down as unconstitutional.

But this gets our constitution and federalism wrong. Just as the states have constitutional authority to make state policy about marriage, so too Congress can pass a federal statute defining a term for federal programs created by federal law. Indeed, Congress has legislated legitimately on marriage more than 1,100 times. DOMA only made clear that Congress meant one man and one woman when it used the words “marriage” and “spouse.”

Some try to argue, then, that what’s really unconstitutional isn’t Congress making this law, but anyone making a law that tells the truth about marriage. That’s what’s at the center of the other case before the high court, the one concerning California’s Proposition 8.

Prop 8 is a state constitutional amendment approved by California voters in 2008 defining marriage for state purposes as the union of one man and one woman. This was the second time that Californians voted in support of marriage within a decade. They voted this second time after the California Supreme Court issued an activist decision redefining marriage — even though state law provided for civil unions for same-sex couples that afforded the same rights and benefits as married couples. Apparently no compromise would be allowed if the lower courts that overturned Prop 8 have their way.

The Prop 8 case provides the Supreme Court with the opportunity to reject faulty arguments that claim that laws defining marriage as between a man and a woman violate the equal protection clause of the U.S. Constitution.

Equality demands that we treat things that are the same in the same ways. But a same-sex relationship is fundamentally different from a marriage. No same-sex union can produce a child. And no same-sex relationship can provide a child with a mother and a father.

And this brings us back to the government’s interest in marriage. Again, that interest is because the act that unites a man and a woman creates new life.

Marriage exists to bring a man and a woman together as husband and wife, to be father and mother to any children their union produces. Marriage is based on the truth that men and woman are distinct and complementary, the fact that reproduction depends on a man and a woman and the reality that children need a mother and a father.

Whatever pollsters and pundits may tell us about “inevitability,” the only way to guarantee a political loss is to sit idly by. Defenders of marriage need to frame our message, strengthen coalitions, devise strategies, and bear witness.

We tend to forget that marriage predates government. Throughout history, diverse cultures and faiths have upheld marriage as the ideal. It is the fundamental building block of all human civilization. Marriage has public purposes that transcend its private purposes.

Marriage is society’s best way to ensure the well-being of children (as I’ve argued at length in this space). State recognition of marriage protects children by encouraging men and women to commit to each other — and to take responsibility for their children.

So it is with good reason that 38 states – not to mention over 90 percent of the countries represented at the United Nations — affirm marriage as the union of a man and a woman, just as diverse cultures and faiths have throughout history.

But whatever any individual American thinks about marriage, the courts shouldn’t be redefining it. Marriage policy should be worked out through the democratic process, not dictated by unelected judges in an activist decision that has no grounding in the text or logic of our Constitution.

- Ryan T. Anderson is the William E. Simon fellow at The Heritage Foundation.