Where in the Constitution does it say that marriage (heterosexual or otherwise) is a right?
(sds asked this question. Here’s an answer.)
Marriage is traditionally in the realm of state’s rights—so we should look at the 14th ammendment.
1. All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the State wherein they reside. No State shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any State deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws.
These two sentences are perhaps the most important and most debated in the Constitution. They do not say that the states must have laws governing things like marriage—but if the states have those laws, they must give everybody equal protection. Some states once had miscegenation laws. As you might imagine, those were unconstitutional under this ammendment. I’m sure some people argued that they should be constitutional—after all, everybody has the same right to marry somebody of the same race. The Supreme Court saw that argument for the garbage it is. (The case, appropriately, is Loving v. Virginia. Mr. and Mrs. Loving sued. Throughout the opinion, they are referred to as “the Loving couple.”)
So the U.S. Constitution doesn’t explicitly state that everybody has a right to marriage. And soon the California Constitution will state that at least one type of marriage is not permissible. But the Constitution does state that if there are going to be laws offering various protections (like spousal priviledges), they have to offer everybody the same type of protection. Some might argue that everybody is equally free to marry somebody of the opposite sex. I would find that one hard to make with a straight face. It’s pretty clear that many people have no interest in marrying somebody of the opposite sex.