To the extent that the United States fought a bloody and protracted civil war in the mid-19th Century over the issue of states' rights, it is fair to say that the issue of federalism versus confederation is part of the American soul. With regard to whether federal law should always take precedence of state laws with which they come into conflict, the answer depends upon the type of state law. On any issue fundamental to the rights guaranteed all U.S. citizens in the Constitution, then preemption is the right and appropriate response. Article VI, Section 2 of the Constitution states that
"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."
As the U.S. Constitution is the preeminent legal document in the country, then its word carries greater legal and moral force than any law or document derived from an individual state's legislature. The above provision from the Constitution is known as the Supremacy Clause precisely because it ensures that federal statute trumps state statute. Because indivdiual states, if left to their own devices, are capable of passing and enforcing laws that conflict with the rights guaranteed under the Constitution, or which can be argued would harm the public, then it is appropriate that the preemption doctrine exists.