In separate action, integrated teams of Freedom Riders rode South on interstate buses. In violation of federal law and the constitution, bus companies had for decades acceded to state laws and required passengers to occupy segregated seating in Southern states. Opponents of the push for integration organized mob violence at stops along the Freedom Ride. In Montgomery, there was police collaboration when a white mob attacked Freedom Riders at the Greyhound Bus Station in May 1961. Outraged national reaction resulted in the enforcement of desegregation of interstate public transportation.