1. Suppose DOMA defined “channels” to mean “navigable-in-fact waterways, as well as all interstate and intrastate waters including (but not limited to) intrastate lakes, rivers, streams (including intermittent streams), mudflats, sandflats, wetlands, sloughs, prairie potholes, wet meadows, playa lakes, natural ponds, drainage ditches, and ephemeral streams,” as Jonathan suggests. Jonathan suggests there would be something unconstitutional here because “the practical effects of this definition would be expand the scope of federal power so as to supplant state authority in an area of traditional state concern.”
I would think, though, that the problem isn’t with the definitional statute itself. For instance, suppose there were such a definitional statute, but it were never used anywhere — presumably no harm, no foul? Or what if it were only used in one statute somewhere in the U.S. Code, where Congress expressed its sense that channels were awesome things, or established a spending program to beautify channels. Again, nothing unconstitutional? I would think that any unconstitutionality would occur if and when that definition gets used in a way that regulates channels beyond what’s allowed under the Commerce Clause or any other source of federal power. So the problem isn’t with the definition but with the specific substantive provision where that definition gets used. There could be no such unconstitutional statutes, or one, or however many, but the fact that DOMA affects hundreds of statutes seems to play no role here.
Getting back to DOMA, I would then doubt that there’s any displacement of state authority as to marriage in any particular statute. Because, take the tax code: Congress didn’t have to grant special tax treatment, say, to married couples; Congress could have written the tax law so joint returns could be filed by any individual “and his blitiri,” where “blitiri” is defined to be “an opposite-sex member of the same union recognized by state law.” Or cut out the state law and imagine a statute with its own definition of “blitiri” cut out of whole cloth, like “a person of the opposite sex with whom the taxpayer has a romantic relationship” or “with whom the taxpayer cohabits” or whatever. Does the argument really hinge on whether the word in the federal statutes is called “marriage,” which happens to overlap with a word that’s used in state family-law statutes?
2. Or would the argument be different in these last two cases? Would the argument be that the tax statute would be unconstitutional on federalism grounds if the definition incorporates an arbitrary subset of state-law marriages, but not if the definition has no reference to state law? I would think that a definition that’s based on an arbitrary subset of state-law marriages (e.g. the limitation of qualifying marriage for immigration purposes to ones that are genuine in some sense, or a hypothetical limitation of some program’s benefits to beneficiaries’ spouses of more than ten years) is probably no less consistent with constitutional federalism than a definition that’s totally independent of state-law marriages, though quite frankly I’d think that in either case there are no constitutional federalism implications from the definition itself.
3. I think I agree that there’s no inherent power to define terms; the definition has to be necessary and proper for carrying out some power. Still, a definition in one statute that applies to hundreds of statutes can be supported by N&P hooked to a different specific federal power in each case, so the definitional statute itself isn’t supported by any one specific power. Suppose it’s true that Congress gave no thought as to whether the definition would make any of those hundreds of statutes work better. But suppose that, magically, the DOMA definition happens to be the most efficient one in each case. Then, I’d think, no harm, no foul, even if Congress put no thought into it. Am I right?
If so, then if there’s some violation of N&P based on the DOMA definition’s making the statute work worse, cost more money, etc., then again that must be because of some particular statute where this happens, not DOMA itself, so the fact that DOMA applies across the board likewise seems to play no role. There might be no such statutes, or one, or however many. Am I correctly interpreting the argument? If so, let’s challenge a particular statute as being beyond Congress’s powers based on the limitation of qualifying spouses, and bring in evidence of how the statute works so poorly that it exceeds N&P bounds, not DOMA itself.
4. Suppose that I’m right about points (1) and (3) and, magically, in all statutes where DOMA applies, i.e., in all statutes that use the term “marriage,” there’s no application that would run afoul of federalism if the DOMA definition had just been pasted in or if the term were called “blitiri,” and in all applications the DOMA definition is the most efficient of all possible definitions. (There are echoes of Leibniz here in more ways than one.) Would it make any difference that the purpose of the statute (either the subjective intent of the lawmakers, or the objective purpose as evidenced by the title of the statute) was to support traditional marriage, which (let’s say) isn’t within a listed power of Congress? I would think no, that would play no independent role. If the purpose of supporting traditional marriage were absent, and someone wrote an opposite-sex restriction into a single statute for some other reason, I’d think the constitutional analysis would go exactly the same, so if this statute were constitutional, DOMA would likewise be constitutional. Or does the argument put independent weight on the purpose? I’d think it shouldn’t.