“Preemption” refers to situations in which a law passed by a higher government authority supersedes a law passed by a lower one. For example, a law passed by a state legislature (or a provision of the state Constitution) supersedes an ordinance passed by a local government, such as a city council. State legislatures are increasingly using preemption laws to block local labor and employment ordinances from taking effect or to dismantle existing ordinances. Ironically, state preemption of labor standards has historically been used for good: to ensure that minimum labor standards are applied statewide. It is only in recent years that it has been so frequently used to take earnings and protections away from workers.
On August 28, 2017, low-wage workers in St. Louis, Missouri, became the latest victims of state preemption laws. St. Louis had raised its minimum wage above the state minimum—but was then forced to lower it back down when the Missouri state legislature preempted the local ordinance.