The courts have ruled that purely intrastate events may affect interstate commerce and are, therefore, subject to federal law. The question is whether or not the Supremes would be willing to overturn United States v. Lopez.
The answer isn't with some state standing up to this nonsense, it's with the rest of the public getting behind a new constitutional amendment correcting judicial abuses concerning the Commerce Clause.
If we don't we will be eternally at the mercy of how the Supremes are stacked.
I think there is wiggle room here. If Montana enacts these laws does it have a substantial effect on interstate commerce? In light of some recent cases (US v. Morrison) I would look forward to this law being tested by SCOTUS. You should read Thomas' dissent in Gonzales v. Raich. It sounds like he wants to overturn Wickard v. Filburn. I hope he can convince some others on the court.
A single amendment clarifying that the rights enumerated in the Fourteenth Amendment refer only to the Freedmen of the post-Civil War era would make it unnecessary to try to undo every single bad Supreme Court decision with a separate amendment. Of course, the Dems would claim the exact opposite of the truth, that such an amendment would be an attempt to reintroduce slavery. Just like them.