During the ACA fight there was considerable discussion of whether the penalty for not carrying personal health insurance was a tax or a fine. The concepts have identical effects; only the wording is different. Yet it seemed to matter a great deal which was which. If there are two laws, one creating a tax and the other a fine with identical effects, is it possible for one to be constitutional and the other not? Is constitutionality in effect alone, or also in wording?
The short answer is ideally, mere phrasing doesn't matter; but in practice, it might.
In general, Justices have been hostile to the notion that mere differences in phasing could result in differences in Constitutionality. For example, in Gonzales v. Raich 545 U.S. 1 (2005), Justice O'Connor wrote in dissent that the majority's opinion would allow Congress to circumvent the requirements of a previous case, U.S. v. Lopez 514 U.S. 549 (1995), via a mere change in wording:
If the Court is right, then Lopez stands for nothing more than a drafting guide: Congress should have described the relevant crime as “transfer or possession of a firearm anywhere in the nation”–thus including commercial and noncommercial activity, and clearly encompassing some activity with assuredly substantial effect on interstate commerce. Had it done so, the majority hints, we would have sustained its authority to regulate possession of firearms in school zones.
Of course, as this suggests, the Court might (as the result of an error) have issued a decision that, if followed faithfully, would result in Constitutional differences resulting merely from a difference in the phrasing of the law -- or worse, a difference in the phrasing of the argument given in favor of or against the law. However, as Chief Justice Roberts explained in his opinion in National Federation of Independent Businesses v. Sebelius 567 U.S. ___ (2012), the Court must try to construe the law in order to avoid this:
Because "every reasonable construction must be resorted to, in order to save a statute from unconstitutionality," Hooper v. California, 155 U. S. 648, the question is whether it is "fairly possible" to interpret the mandate as imposing such a tax.
In other words, phrasing shouldn't matter; the Court is supposed to ignore phrasing and construe a statute however it can despite its specific phrasing to see if the statute is Constitutional.
We can demonstrate further than the Constitutionality of a statute is dependent on its effects -- and not its phrasing -- by examining some of the judicial tests used to determine Constitutionality. Though there are hundreds, if not thousands, such tests, we can examine two of them in particular: rational basis review, and strict scrutiny.
Rational basis review and strict scrutiny are generic tests applying to almost every law; indeed, a number of other judicial tests are simply instantionations of these tests that refine the inquiry under more specific circumstances. By demonstrating that these tests aren't dependent on a law's phrasing, we can show that the Court does not (at least as a general matter) take it into account.
All laws must at least satisfy rational basis review, which is incredibly deferential. In short, it asks whether there the law can reasonably be believed to have any connection to a legitimate government purpose. For state governments, a law must be related to the state's broad police powers; for Federal legislation the law must be related to one of the Federal governments enumerated powers under the first three Articles of the Constitution.
John Marshall first articulated the test for determining whether legislation is rationally related to one of the legislature's enumerated powers in McCulloch v. Maryland, 17 U.S. 316 (1819). This test is deferential to the government, and looks to the legislation's purpose and effects, rather than examining its specific phrasing:
Let the end be legitimate, let it be within the scope of the Constitution, and all means which are appropriate, which are plainly adapted to that end, which are not prohibited, but consist with the letter and spirit of the Constitution, are Constitutional.
Rational basis analysis for state legislation is similarly deferential, but not all legislation is subject to the rational basis test. Some legislation, such as legislation that appears to infringe on Constitutionally protected rights, or discriminates against discrete and insular minorities, is subject to strict scrutiny. The test of strict scrutiny was first articulated in a footnote, footnote 4, in United States v. Carolene Products Co., 304 U.S. 144 (1938).
Strict scrutiny requires that a law be necessary to further a compelling government interest, and be the least restrictive means of doing so. Though far less deferential than rational basis review, strict scrutiny still analyzes the effects and the purpose of the law, rather than its specific phrasing.
Given that Justices are hostile to the prioritization of a law's wording over its effects, and given that judicial tests look at the laws purpose and its effects (rather than its text independently of those things), it is fair to conclude that what really matters to the Court are what the law does, not what language it uses to express it. Of course, it can sometimes be difficult to distinguish between a matter of phrasing and a matter of actual effects, so phrasing may matter regardless.