Preemption occurs when a “higher” level of government eliminates or reduces the authority of a “lower” level to legislate in a certain area. Under the Supremacy Clause of the U.S. Constitution, Congress and federal regulators have virtually unlimited authority to preempt state and local health laws. Similarly, states generally have broad authority to preempt local laws. The most effective public health policies typically begin at the local level where they are tested and improved upon, before being adopted by states. When local control is eliminated, this process of developing strong public health policies is lost. This top-down, one-size-fits-all approach often increases health disparities and reduces health equity.