Does federal law operate to the exclusion of state law?

But despite the lack of express congressional design, federal law by implication may operate to the exclusion of state law "where compliance with both federal and state regulations is a physical impossibility" or where there is an "impossibility of dual compliance resulting in an inevitable collision between the two schemes of regulation, ..." (Florida Avocado Growers v. Paul, supra, 373 U.S. at pp. 142-143, 83 S.Ct. at pp. 1217-1218.)