Do reasons for non-enforcement matter?

The Eighth Circuit declared invalid a Missouri law that a bunch of federal laws related to firearms "shall be invalid to this state, shall not
be recognized by this state, shall be specifically rejected by this state, and shall not be enforced by this state." No state or local officials possess enforcement authority. And the law creates a private right of action (because Republican lawmakers believe that is the magic bullet to stop everything they do not like) against any public official who enforces the law.

Missouri argued (correctly) that it can refuse to allow its officers to enforce federal law; thus, the reasons for refusing to enforce do not matter. Here, in full, is the Court's response:

That Missouri may lawfully withhold its assistance from federal law enforcement, however, does not mean that the State may do so by purporting to invalidate federal law. In this context, as in others, the Constitution “is concerned with means as well as ends.” Horne v. Dep’t of Agric., 576 U.S. 350, 362 (2015). Missouri has the power to withhold state assistance, “but the means it uses to achieve its ends must be ‘consist[ent] with the letter and spirit of the constitution.’” Id. (quoting McCulloch, 7 U.S. (4 Wheat.) at 421) (alteration in original). Missouri’s assertion that federal laws regulating firearms are “invalid to this State” is inconsistent with both. If the State prefers as a matter of policy to discontinue assistance with the enforcement of valid federal firearms laws, then it may do so by other means that are lawful, and assume political accountability for that decision.

I am a formalist and even I recognize this as utterly mindless formalism. This is not 1833 South Carolina preparing to wield the militia against federal enforcers. There is no meaningful difference between "federal law is illegal in this state and we will not enforce it" and "federal law is stupid and we will not enforce it" and "we don't wanna enforce it just 'cause and you can't make us--nyah." Missouri can reenact the identical law tomorrow and rely on #2 or #3 and land in the same place--no state or local enforcement, private right of action against any officer who attempts to enforce.

Maybe the law could include a preamble or finding saying "We, the legislature, believe these laws are invalid to this state, should not be recognized by this state, should be specifically rejected by this state, and shall not be enforced by this state, but the activist federal judges will not let us say that."