"The physical-presence rule sits upon a foundation of essentially factual premises, frozen in time, about the burdens of collecting sales tax and the likelihood that the rule will promote or undermine the goals of the dormant commerce clause. Those factual premises have now been reversed; the “tides of time” have now comprehensively 'wash[ed] away' whatever foundation Quill’s rule ever had," said the state in its brief. 

Wayfair, along with co-defendants Newegg and Overstock, however, argued in their brief that overturning Quill would present an excessive compliance burden for online sellers, especially given that they would need to deal with the widely varying laws of multiple jurisdictions at once, arguing that South Dakota is pretending these burdens don't exist. They argued that Congress would be better suited to address this issue than state governments. Further, they were skeptical of the "times have changed" argument presented by South Dakota. 

"Changed conditions in the retail marketplace also cannot justify the abrogation of the physical presence rule where the constitutionally-significant conditions– undue burdens derived from excessively complicated state sales tax systems– remain unchanged," said the defendants. 

At stake in this case are billions of dollars in potential revenue. The GAO estimated in a recent report that if states were able to tax all online sales from remote sellers, then they would collect $8 billion to $13 billion in additional revenues, though warned that it could impose compliance costs on businesses.