Jeff Jacoby writes in the Boston Globe in the wake of New York's attempt to redefine marriage:

When the Supreme Court ruled in June 1967 that Virginia’s law penalizing interracial marriage could not stand, it was not changing the fundamental and enduring meaning of marriage: It was affirming it. It was upholding the integrity of marriage by protecting it from irrelevant — and unconstitutional — racial manipulation. Virginia had interfered with the core elements of marriage in order to promote white supremacy, a value completely alien to marriage. Marriage is designed to bring men and women together; anti-miscegenation laws frustrated that design, and could not stand.

Same-sex marriage, too, interferes with the core elements of wedlock in order to advance an unrelated goal — the dignity and equality of gays and lesbians. The fact that many decent people ardently embrace that goal doesn’t change reality: The essential, public purpose of marriage is to unite male and female — to bind men and women to each other and to the children that their sexual behavior may produce. It is rooted in the belief that every child needs a mother and a father. Gay marriage, whether enacted by lawmakers or imposed by judges, disconnects marriage from its most basic idea. Ultimately, that isn’t tenable either.

The old laws banning interracial marriage had a long run but they eventually collapsed. The new laws in New York and some other states authorizing same-sex marriage may be destined for a long run as well, but I suspect they too will likely eventually collapse. Marriage — male-female marriage — is indispensable to human welfare. That is why it has existed in virtually every known human society. And why it cannot be permanently redefined.