The tax evasion comes in when you fail to pay the use tax due and make false declarations or intentionally omit information when you make representations to the government (i.e. in tax filings).
The individual in question could have set up a Montana LLC, purchased a vehicle through it, paid the use tax due when he moved it to Tennessee and changed the registration within the 30 day limit.
Of course, there is no benefit of going out of your way to buy a car in Montana if you don't intend to drive it there, but the charges against this person relate to his failure to pay tax, not the mere fact that he set up an LLC.
If its just a monetary fine then there’s little reason to arrest somebody to immediately release them when you could’ve just told the accountant he needs to pay a fine or he’s going to be arrested.
It's akin to intentionally defrauding the state.
A quick Google search indicates that willful tax evasion is a Class E felony in Tennessee, with a potential prison term of 1-6 years.
The parent commenter seemed to be saying that if you could reduce your tax burden by putting something through a business then that's illegal even if you've not broken any specific laws.
Gregory v. Helvering, decided by the US Supreme Court in 1935.
Edit: So if it's a legal arrangement that reduces taxes, then yes, it's legal.
https://www.canada.ca/en/revenue-agency/programs/about-canad...
TLDR: if the only reason for a transaction is tax avoidance, it may not be "illegal", but it may be disallowed (and presumably incorporated in subsequent legislation).
Similar is "wash sale" legislation: for example, selling a security for a tax loss and
- buying it back within 30 days
- buying a call option on that security.
I will guess that the former might get you just a reassessment (the first time). The latter... well, you're smart enough to know about options and tax-loss sale, now you need to demonstrate that you didn't do it for tax avoidance.
Not sure what US law (federal and gazillion states) has on this.