The constitutional issue at the heart of California's ban on same-sex marriage, which the U.S. Supreme Court considered Tuesday, and the federal Defense of Marriage Act, which will come before the high court today, is not limited to gay marriage, or marriage in general.
The 14th Amendment to the Constitution guarantees "the equal protection of the laws" to all people in the United States. The amendment says that no state may deny such protection; for example, a state may not require one group of people to do one list of things to obtain a driver's license, and another group to meet another set of requirements entirely.
In the two cases, the court should declare there is one form of marriage for all Americans -- equal protection -- and that each state must comply with the Constitution. One law for all, or no form of marriage for anyone.
The Defense of Marriage Act is a case of separate and unequal. California's Proposition 8 is a matter of one state doing its own thing.
But marriage is a legal contract. As a matter of constitutional law, it must be available to all citizens in all states, not prohibited for some and offered in a lesser form for others. There cannot be two forms of the marriage contract, any more than there can be two forms of voting or free speech.
The Supreme Court may deem Proposition 8's voluntary and vociferous defenders to lack standing. So the court may dismiss the California case without even getting to its merits.
But the Defense of Marriage Act is a federal law that violates the federal Constitution. The Obama administration's Justice Department has rightly refused to enforce the law. Last week, a federal judge in New York ruled that the law violates the Constitution because it required a woman to pay federal tax on her same-sex spouse's estate, while opposite-sex spouses are exempt.
The law does not pass the equal-protection test. Marriage involves many rights and obligations; the existence of two legal forms of marriage creates a domino effect of inequalities.
The only kind of equality achievable in this world is equality before the law. Fair play is the whole point of our system of law. Otherwise, it is not law at all, but a series of arbitrary privileges and immunities that are inconsistently applied.