Bensing Company manufactures generic drugs for the treatment of heart disease. A federal law requires generic drug makers to use labels that are identical to the labels on brand-name versions of the drugs. Hunter Rothfus purchased Bensing's generic drugs in Ohio and wants to sue Bensing for defective labeling based on its failure to comply with Ohio state common law (rather than the federal labeling requirements).What defense might Bensing assert to avoid liability under state law?