Here is a situation for Don and Joan who are partners for a vending cart business, which sells hotdogs on the street. Joan and Don received a mailed notice from the City of Richmond informing them that, due to a new City Ordinance brought about because of excessive traffic flow, licensed street vendors would no longer be able to set up in the immediate downtown area of Richmond. The city passed the ordinance at the last city council meeting without prior notice of any kind. Vendors could only sell their wares in a concentric circle some 15 blocks from the main street of Richmond. Define the constitutional law theory that would help Joan and Don to defeat the law and its application to their business.