The tenth amendment confirms that any power not delegated to the feds by the Constitution or prohibited to the states belong to the states and the people of those states. So any federal act that clearly assumes unconstitutional power (there are many such acts) are ACTUALLY powers of the states. So constitutional state sovereignty as confirmed by the tenth amendment allows nullification and voiding unconstitutional federal acts because those acts impinge upon the constitutional powers of the states.
Law school makes no distinction about federal law. There you're taught that generally all federal law is superior to state law (with the caveat of the Erie Doctrine). (But then law school doesn't really teach you the Constitution as written an originally understood an intended.)
But the Constitution does make a distinction about federal law.
This Constitution, and the Laws of the United States which shall be made in Pursuance thereof...shall be the supreme Law of the Land. (Id.)
If Congress passes constitutional ("in pursuance") legislation then that legislation is the supreme (or "superior") law of the land. The states have no constitutional grounds to reject such law and that has been the problem is times past with so-called state nullification.
But if Congress does not legislate according to and within the confines of the Constitution, then their legislation is not "made in pursuance and, therefore, not constitutionally the supreme (or superior) law of the land. In that case, the states, or another federal branch, may challenge the act with reasonable constitutionally-based rationale.