Federal drug regulations, as interpreted by the FDA, prevent the manufacturer of a generic drug from independently changing the safety label. In general, a manufacturer seeking federal approval to market a new drug must prove that it is safe and effective and that the proposed label is accurate and adequate. Although the same rules originally applied to all drugs, the 1984 law commonly called the Hatch–Waxman Amendments allows a generic drug manufacturer to gain FDA approval simply by showing that its drug is equivalent to an already-approved brand-name drug, and that the safety and efficacy labeling proposed for its drug is the same as that approved for the brand-name drug. Respondents argued that Federal Law nevertheless provides avenues through which the manufacturers could have altered their metoclopramide (Reglan) labels: (i) the FDA’s “changes-being-effected” (CBE) process, which permits drug manufacturers, without pre-approval, to add or strengthen a warning label; and/or (ii) sending “Dear Doctor” letters providing additional warnings to prescribing physicians and other healthcare professionals. However, the FDA denies that manufacturers could have used either of these processes to unilaterally strengthen their warning labels. The Court defers to the FDA’s views because they are not plainly erroneous or inconsistent with the regulations, and there is no other reason to doubt that they reflect the FDA’s fair and considered judgment. Assuming, without deciding, that the FDA is correct that Federal Law required the manufacturers to ask for the agency’s assistance in convincing the brand-name manufacturer to adopt a stronger label, the Court found preemption based on impossibility: If the manufacturers had independently changed their labels to satisfy their State Law duties to attach a safer label to their generic metoclopramide, they would have violated the Federal requirement that generic drug labels be the same as the corresponding brand-name drug labels. Thus, it was impossible for them to comply with both State and Federal law. And even if they had fulfilled their Federal duty to ask for FDA help in strengthening the corresponding brand-name label, (assuming such a duty exists), they would not have satisfied their State tort-law duty. Pliva v. Mensing, 131 S.Ct. 2567 (2011).