Preemption refers to a part of the US Constitution that says that federal law is the supreme law of the land. So that basically means that when federal law and state laws are in conflict, federal law wins, federal law trumps. So in the context of devices, there's a provision in a federal law, in the Federal Drug and Cosmetic Act, that talks about how states cannot have additional or different requirements from federal law with respect to the safety and effectiveness of certain devices. So preemption could be either expressed or implied. So if it's expressed there's something in a federal statute that Congress has passed, and the president has signed, and it's become federal statutory law or something in one of those laws that expressly explicitly says that state law is preempted, is trumped by federal law. There are a number of different ways that one might argue that state law is impliedly preempted by federal law. The implied preemption arguments being that there is nothing that is explicitly written in a federal statute about preemption, but nevertheless you can conclude that Congress intended to display state law through some other means. In the device context we're talking about expressed preemption, the first kind, because the Federal Food Drug and Cosmetic Act has this provision that says that states and other subdivisions of counties, cities, whomever, cannot impose additional or different requirements on devices; requirements that are additional or differ from federal requirements and relate to the safety and effectiveness of certain devices. And in a case called Riegel v. Medtronic, the Supreme Court said that this provision really applies only to devices approved through the pre-market approval process. So through the PMA process. So it's for a subset of devices that go through the PMA process. And in those cases, and the Supreme Court in Riegel interpreted the provision of the Federal Food Drug and Cosmetic Act to preempt state tort law. So even state laws that are not statutory, even these lawsuits between private parties can be preempted under this provision of the Federal Food Drug and Cosmetic.