Let's begin with a few words about the Dormant Commerce Clause and how it interacts with federalism principles.

The U.S. Constitution presumptively preserves state authority to control what happens within state borders, especially state power to protect citizens and residents from what legislators or voters perceive as harms. This state "police power" to regulate "health, safety, and morals" is implicitly acknowledged by the Constitution's struc­­­ture of enumerated powers, and by the Tenth Amendment.[1]

The Constitution's preservation of the police power in the states ensures that "the facets of governing that touch on citizens' daily lives are normally administered by smaller governments closer to the governed."[2] Regulatory preferences differ across states because states differ in their citizens' tastes, moral views, wealth, willingness to pay, and the like. State lawmakers are generally better positioned than federal lawmakers to ascertain such in-state preferences and implement the best policies based on them. Because policy preferences differ across states, regulating at the state level can in the aggregate satisfy more individual preferences than a uniform national law.[3] And federalism also lets states serve as "laboratories" that can experiment with various options, and show the way for other states (and perhaps for an eventual national rule).