The Court determined that federal Occupational Safety and Health Administration regulations preempted various Illinois provisions for licensing workers who handled hazardous waste materials.

It argued these statutes were preempted by the Occupational Safety and Health Act and Occupational Safety and Health Administration regulations implementing a requirement of the Superfund Amendments and Reauthorization Act of 1986 which also standards to train workers who handle hazardous wastes.

The claim was brought against petitioner Gade's predecessor as director of the state environmental protection agency.

1447 (1947)), and conflict pre-emption, where "compliance with both federal and state regulations is a physical impossibility," Florida Lime & Avocado Growers, Inc. v. Paul, 373 U.S. 132, 142-143, 83 S.Ct.

Our ultimate task in any pre-emption case is to determine whether state regulation is consistent with the structure and purpose of the statute as a whole.

1549, 1555, 95 L.Ed.2d 39 (1987) (internal quotation marks and citations omitted), we hold that nonapproved state regulation of occupational safety and health issues for which a federal standard is in effect is impliedly pre-empted as in conflict with the full purposes and objectives of the OSH Act.

The Act as a whole demonstrates that Congress intended to promote occupational safety and health while avoiding subjecting workers and employers to duplicative regulation.

This intent is indicated principally in § 18(b)'s statement that a State "shall" submit a plan if it wishes to "assume responsibility" for developing and enforcing health and safety standards.

The language and purposes of §§ 18(a), (c), (f), and (h) all confirm the view that the States cannot assume an enforcement role without the Secretary's approval, unless no federal standard is in effect.

Justice Kennedy concurred but thought that Congress had expressly preempted this area and that the application of implicit preemption in this case expanded the doctrine too far.

Such a finding is not contrary to the longstanding rule that this Court will not infer pre-emption of the States' historic police powers absent a clear statement of intent by Congress.

Unartful though § 18(b)'s language may be, its structure and language, in conjunction with subsections (a), (c), and (f), leave little doubt that in the OSH Act Congress intended to pre-empt supplementary state regulation of an occupational safety and health issue with respect to which a federal standard exists.

We have held, in express pre-emption cases, that Congress' intent must be divined from the language, structure, and purposes of the statute as a whole.

Though he agreed with Justice O'Connor that there were three categories of preemption (express, field, and conflict) he believed that congress must "unmistakably ordain" to preempt state law.

He felt the majority's strongest argument was that the regulations contained a "saving clause" which stated that any issues not spoken on were not preempted.