One favored method of dismissing the sovereignty of state governments is to quote the Supremacy Clause, saying that since the Constitution is the supreme law of the land that state laws are necessarily subordinate to federal law. The only problem with this reading is that they fail to read the entire Supremacy Clause.
To remedy this I will paste the Supremacy Clause into this post here. “This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; and the Judges in every State shall be bound thereby, any Thing in the Constitution or Laws of any State to the Contrary notwithstanding.“
According to my reading of this clause, only the laws which are made in pursuance of the Constitution are supreme, therefore, unconstitutional laws (which nullification laws are enacted to repeal) are not supreme- and in my view are illegal to pass at all.