The supreme law of the land is a term best described as the highest form of law a nation can have. It is the foundation upon which all the other laws are built upon and legally established. For the United States of America, the supreme law of the land is its constitution, federal laws, and all the treaties, unless they are in direct conflict with the constitution itself.
The constitution is, therefore, the founding pillar of the entire political existence of the united states of America.
The Supremacy Clause
Where is this actually established? It is in Clause 2 of Article VI in the United States Constitution. The common nickname for that section is "The Supremacy Clause," which is also the only place this term was ever used in the entire Constitution. It says that the federal government is supreme over the state laws, and thus all state judges are obligated to uphold the clause. This is true even in situations of conflict with the state laws.Supremacy Clause is meant to regulate any possible legal conflicts, i.e., the shared governance between national law and state law. However, the federal government or the states address anything they plan on doing; they are always under the authority of the Constitution. This doesn't mean the state laws do not hold any bargain. As long as they are abiding the national laws, they can authorize policies on healthcare, education, and taxes, just like the federal government can.
This relation between the federal government and the states was clearer in the past. Still, ever since the 1860s and the American Civil War, the exclusive and concurrent powers of federal and state began overlapping. Even today, the questions of federalism in the United States is the source of much controversy and dilemmas. Questions about the control of healthcare and education, for example, are one of those controversial topics.