Preemption: whether, in fact, the state tort action conflicts with the federal regulation: Under ordinary conflict pre-emption principles a state law that “stands as an obstacle to the accomplishment” of a federal law is preempted. Hines v. Davidowitz, 312 U. S. 52, 67. In Geier, the state law stood as an obstacle to the accomplishment of a significant federal regulatory objective, namely, giving manufacturers a choice among different kinds of passive restraint systems. This conclusion was supported by the regulation’s history, the agency’s contemporaneous explanation, and the Government’s current understanding of the regulation. The history showed that the Department of Transportation (DOT) had long thought it important to leave manufacturers with a choice of systems. DOT’s contemporaneous explanation of the regulation made clear that manufacturer choice was an important means for achieving DOT’s basic objectives. It phased in passive restraint requirements to give manufacturers time to improve airbag technology and develop better systems; it worried that requiring airbags would cause a public backlash; and it was concerned about airbag safety and cost. Finally, the Government’s current understanding was that a tort suit insisting upon airbag use would “ ‘ “stand as an obstacle to the accomplishment and execution of these objectives.” ’ ” 529 U. S., at 883; like the regulation in Geier, the instant regulation leaves the manufacturer with a choice, and the tort suit here would restrict that choice. But in contrast to Geier, the choice here is not a significant regulatory objective; many federal safety regulations embody a cost effectiveness judgment. To infer pre-emptive intent from the mere existence of such a cost-effectiveness judgment would eliminate the possibility that the agency seeks only to set forth a minimum standard (U.S.S.Ct., 23.02.11, Williamson v. Mazda, J. Breyer).