Other regions of the West are conquered through a series of wars with other colonial nations, and Native Americans. Virtually all the land from the Allegheny Mountains to the Pacific Oceans was once owned by the federal government. Large amounts of that land was later given to new Western states. Constitution is the supreme law of the United States. It has evolved over time.
Several clauses form the basis of federal environmental policy in America.
Allows federal government to regulate interstate and foreign commerce. Trade across state and national boundaries is common. Federal law prevails over state law when they conflict. This is the basis of the preemption doctrine. Federal law preempts state law if federal law supersedes state law, or if area is Constitutionally reserved for federal authority alone.