There are two types of preemption- express preemption and implied preemption. Express preemption occurs when a legislature expressly states that only the state can pass an ordinance, and that localities are forbidden from passing them. Implied preemption, on the other hand, is raised when a legislature has been silent on the issue.
Almost without fail, opposition will file an implied preemption claim if an ordinance is the first one in a state, claiming that the legislature, while not explicitly stating that the locality does not have the authority to pass it, surely meant it. Courts look at legislative history and other legislative information to determine what the legislature's intent was when dealing with tobacco issues. Several states have been ruled impliedly preempted by courts, thereby losing any local smokefree ordinances that may have been passed. To see if your state is preempted, visit Protect Local Control.
It is crucial that any state bill that is being discussed in your state capitol have an anti-preemption clause within the bill. If the bill is passed, it gives courts a clear message that the legislature did not intend to preempt the ability of local governments to pass smokefree ordinances.