Rejecting Pfizer’s argument that it would have been impossible for the drug manufacturer to comply with a State Law “duty” to modify the drug Phenergan’s labeling without violating Federal Law, the Court noted that when a manufacturer is changing a label to “add or strengthen a contraindication, warning, precaution, or adverse reaction” or to “add or strengthen an instruction about dosage and administration that is intended to increase the safe use of the drug product,” it may make the labeling change upon filing its supplemental application with the FDA, and need not wait for FDA approval. “Of course, the FDA retains authority to reject labeling changes made pursuant to the CBE regulation in its review of the manufacturer’s supplemental application, just as it retains such authority in reviewing all supplemental applications. But absent clear evidence that the FDA would not have approved a change to Phenergan’s label, we will not conclude that it was impossible for Wyeth to comply with both federal and state requirements.” Then, rejecting the 2006 Preamble, the Court noted that “we have not deferred to an agency’s conclusion that state law is pre-empted. Rather, we have attended to an agency’s explanation of how state law affects the regulatory scheme. The preamble is at odds with what evidence we have of Congress’ purposes, and it reverses the FDA’s own longstanding position without providing a reasoned explanation, including any discussion of how state law has interfered with the FDA’s regulation of drug labeling during decades of coexistence.” Wyeth v. Levine, 555 U.S. 555 (2009).