In 1992 the Supreme Court of the United States settled lower court rulings in favor of out of state businesses. It is ruling, it stated that an out-of-state retailer must have a presence (Nexus) in the state for the state to force the retailer to collect sales tax. Typically this presence was defined as an office or warehouse.
With the emergence of Amazon FBA, states are trying to redefine Nexus. There are several cases in lower courts that may find their way to SCOTUS for clarification.
The full text and opinions about Quill Corp. v. North Dakota, 504 U.S. 298 case can be found here.