Marbury v. Madison, 5 US 137,(1803) "The Constitution of these United States is the supreme law of the land. Any law that is repugnant to the Constitution is null and void of law."
Murdock v. Penn., 319 US 105, (1943) "No state shall convert a liberty into a privilege, license it, and attach a fee to it."
Shuttlesworth v. Birmingham, 373 US 262, (1969) "If the state converts a liberty into a privilege, the citizen can engage in the right with impunity."