In the case of Delbert Williamson, et al. v. Mazda Motor of America, Inc., et al., 2010, the U.S Supreme Court ruled in favor of Mazda. The case was brought by the family of Thanh Williamson who died in a car accident while wearing a lap belt in the middle rear seat as per federal regulations at that time (1989). The Williamsons argued that Mazda should have installed lap-and-shoulder belts and their failure to do so made them liable for her death under state tort law. However, Mazda countered this argument stating they were following federal safety standards which allowed either type of belt to be installed during manufacturing. The court held that compliance with federal motor vehicle safety standards does not necessarily exempt auto manufacturers from liability under state common law tort actions if those manufacturers could have opted for safer but more expensive equipment options permitted by Federal Law. But it also stated that preemption did not apply here because there was no significant objective conflict between federal regulation and state law since automakers had choices about seatbelt types.

In the dissenting opinion for Williamson v. Mazda Motor of America, Justice Thomas argued that federal regulations should preempt state tort law claims. He contended that a vehicle manufacturer's decision to install lap-only seatbelts in some rear seats was made under a standard set by the Federal Motor Vehicle Safety Standard (FMVSS) 208, which allowed manufacturers to choose between installing lap-only or shoulder-and-lap belts. Therefore, he believed it was inappropriate for states to penalize manufacturers for making choices explicitly permitted by federal regulation. In his view, allowing such lawsuits would undermine uniformity and could discourage automakers from offering optional safety equipment not required by federal standards out of fear they might be sued if they do not make those options standard on all vehicles.