Far from effecting any departure from past practice, DOMA merely reaffirmed and made crystal clear what Congress had always meant by the term “marriage” in provisions of federal law: a male-female union. DOMA doesn’t intrude at all on a state’s authority to regulate marriage under state law. It doesn’t nullify or prohibit any marriages, or in any other respect preempt the operation of state law. On the contrary, it leaves the states free to define, or redefine, marriage as they please. That point is illustrated by the fact that nine states (as well as the District of Columbia) have adopted same-sex marriage since DOMA’s enactment.
DOMA’s definition of marriage merely establishes what marriage is for purposes of provisions of federal law. Under our system of federalism, the states and the federal government have sovereign authority over their respective domains. Thus, DOMA respects and implements federalism by exercising the federal government’s authority over federal law.
Congress has often found it convenient to use state-law marital status in federal laws and programs. But it has never accepted state-law marital status as constraining how those laws and programs operate, and there is no reason that it should. For example, under provisions of the Internal Revenue Code, a person who is legally separated from his spouse, but not yet divorced, is treated as unmarried, as is a person whose spouse is a nonresident alien. Likewise, under the immigration laws, a marriage entered into for the purpose of gaining an immigrant’s admission will be disregarded even though that marriage remains valid under state law. How could anyone imagine that federalism means that a state’s authority to regulate marriage for state-law purposes should intrude on how the federal government operates in these and other areas?
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DOMA’s challengers contend that the federal government’s interest in uniform eligibility is somehow undercut by the fact that DOMA ignores variations in state marriage laws on matters such as age of consent and permitted degrees of consanguinity. But this shows only that DOMA distinguishes between the components of marriage that the federal government regards as essential and those it regards as incidental. DOMA’s challengers accept this same distinction as reasonable, as they don’t object to DOMA’s requirements that a marriage be a legal union and that it be between two persons. Where they differ is only in their insistence that it is illegitimate to regard the male-female component of DOMA’s definition as an essential attribute of marriage — the very point at the heart of the constitutional attack on state marriage laws.