Preemption of State laws; concurrent jurisdiction; prohibition on certain State action

No provision of this chapter shall be construed as indicating an intent on the part of the Congress to occupy the field in which such provision operates to the exclusion of the law of any State on the same subject matter, unless there is a direct and positive conflict between such provision and the law of the State so that the two cannot be reconciled or consistently stand together. Nor shall any provision of this chapter be construed to exclude the Federal Government from enforcing the provision of this chapter within any State, whether or not such State has enacted legislation on the same subject, it being the intent of the Congress to establish concurrent jurisdiction with the States over such subject matter. In no case shall any such State take any action pursuant to this section involving a violation of any such law of that State which would preclude the United States from enforcing the provisions of this chapter against any person.