The interesting one is Tax Violations. Tax Violations are Federal Felonies. But, take a close look at the wording of the Constitution.
The exact amendment was designed to prevent a Poll Tax on Blacks, but the wording is broad enough to allow felons to vote if their offense was a tax violation.
Amendment XXIV
Section 1. The right of citizens of the United States to vote in any primary or other election for President or Vice President, for electors for President or Vice President, or for Senator or Representative in Congress, shall not be denied o r abridged by the United States or any state by reason of failure to pay any poll tax or other tax.
Section 2. The Congress shall have power to enforce this article by appropriate legislation.
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If this were to be upheld in SCOTUS, then the Government would have to do something. A felony denies the right to vote. So, theoretically, no tax violation including an NFA Violation could be considered a Felony. The Federal Government only has Felonies, so there could be no Federal Tax Laws. The snowball effect would be the voiding of all tax laws including the NFA until such time as the situation could be remedied by changing the law, if it could even get done.