This dreaded clause was placed into the fourteenth amendment which basically destroys a states ability to interfere with the fourteenth amendment since any state law that attempts to do so will simply be overridden by a federal law that was made in pursuance of that particular power. The same clause also exist for amendments thirteen, fourteen, fifteen, eighteen, nineteen, twenty-three, twenty-four, and twenty-six which makes it impossible for states to interfere or legitimately enforce those particular amendments because any federal law that does so would be superior to a state law that attempts to do the same thing. This means that states can’t enforce these amendments in any meaningful way since any federal law that does so would override any state law made with the same power and this may seem like an argument against state nullification but it actually provides the strongest justification for state nullification.
When the people who wrote those amendments gave that power to the federal government they established that the power to enforce the constitution legislatively does exist. It can not be denied that such a power exists because it is plainly written into it so the only question left is who has that power. Is it the states or the federal government? It is clearly given to the federal government for those amendments listed above but where it was not delegated to the federal government it is squarely reserved to the states. The federal government only has the power to enforce those particular amendments but where that power was not delegated to the federal government and/or where it is not prohibited by the constitution then that power rightfully belongs to the states. The power to enforce the constitution has not been denied to the states by the constitution and the federal government only has that power for a few sections of the constitution which means that under the tenth amendment states have the legal ability to enforce the constitution where it has not been granted to the federal government.
One of the most damaging arguments against nullification is that it is a back-door attempt to deny people the right to vote but it is not possible for any state to legislatively deny people basic voter protections guaranteed by the fourteenth amendment because the fourteenth amendment granted the federal government the power to enforce that amendment with appropriate legislation. This should silence all detractors of nullification that bring about absurd talking points that tenthers are trying to deny people their right to vote because any attempt by a state will be overridden by the federal government’s own legislation. Federal law has supremacy in this scenario so it is not possible to use nullification for that purpose.
I personally suspect that the whole reason why this clause was added was to make sure that the newly re-admitted southern states would not try to interfere with a person’s right to vote. This clause may give some credence to those who say that states can’t legislatively enforce the constitution (or what we call nullification) but this is only true for the fourteenth amendment and other amendments that have a similar clause. In cases, such as the fourteenth amendment, where the federal government has the power to enforce with appropriate legislation the federal government will have the last say but in every other section of the constitution it does not. That power was not delegated to the federal government and where that power does not exist it falls to the states. This means that states have the power to enforce the constitution with appropriate legislation where it hasn’t been delegated to the federal government (or prohibited to them by the constitution) which means that individual states have the power to enforce the constitution with appropriate legislation which gives them the final say over those areas of the constitution.
This is the strongest justification for state nullification because we can easily say that the federal government has the power to enforce the constitution with appropriate legislation for the fourteenth amendment but it is not possible to say that such a power exist for every other aspect of the constitution. There is no text, sentence, or clause that gives the power to the federal government to properly enforce the first amendment, the second amendment, the fourth amendment, and almost every other area of the constitution which means it must belong to the states themselves. This allows states to use that power to enforce the constitution as they see fit for any section of the constitution where it was not delegated to the federal government which allows them to void any federal law that they believe violates the constitution.