Federal preemption of state tort law actions brought against drug and medical device manufacturers, which has the legal effect of immunizing manufacturers from tort liability, has been a source of great controversy in recent years. These cases arise when individuals are allegedly harmed by a defective product and sue the manufacturer. The Federal Food, Drug, and Cosmetic Act (FDCA) does not expressly allow these injured individuals to bring such a claim, and, accordingly, someone injured by a medical device or drug may be limited to bringing a suit under state tort law in order to obtain compensation for the resulting injuries. For example, an injured plaintiff may allege that a manufacturer was negligent with respect to the design of the drug or device and seek monetary relief for the injuries suffered. However, because of the doctrine of constitutional preemption, a court may dismiss such a claim because the claim is superseded by federal law. The Supreme Court has evaluated medical device and drug preemption cases on a number of occasions over the past two decades, and the results have been mixed: in some instances a person injured by an allegedly dangerous drug or device is barred from suing a manufacturer, whereas in other cases, the Court has allowed a suit to go forward. In order to explain the major Supreme Court cases in this area of law, this report begins by providing background on three general subject matters. First, the report examines the doctrine of constitutional preemption, the legal basis for determining when a state law must yield to a federal law. From there, the report discusses both the state law and federal laws at issue in the recent Supreme Court FDCA preemption cases. Specifically, the report addresses the types of state-law tort claims that are commonly brought against drug and medical device manufacturers. After discussing preemption and tort liability, the report examines federal law regulating prescription drugs and medical devices. With the background on the general subjects of preemption, tort law, and federal regulation of drugs and devices in mind, the report concludes by examining the major Supreme Court FDCA preemption cases and analyzing possible judicial and legislative developments that may affect this complicated and ever-changing area of law. Because of the Supremacy Clause found in Article VI of the Constitution, the "Laws of the United States" made in pursuance of the Constitution are by definition "the supreme Law of the Land" "notwithstanding" "the Constitution or the Laws of any State to the Contrary." Under the doctrine of federal preemption, state laws are invalid if they "interfere with, or are contrary to federal law." Accordingly, preemption is a necessary product of a specific federal law's reach, and, in that vein, the Court has repeatedly recognized that the intent of Congress is the "'ultimate touch-stone' in every pre-emption case." Another principle that sometimes guides the Supreme Court's jurisprudence in preemption cases is the so-called "presumption against preemption." Specifically, the Court in the past has held that in "all pre-emption cases" an assumption exists that "the historic police powers of the States were not to be superseded by [a] Federal Act unless that was the clear and manifest purpose of Congress." Notwithstanding the Court's previous pronouncements regarding the presumption against preemption, in recent terms, the Court arguably appears to be moving away from embracing the presumption. Following Wyeth v. Levine , the presumption has largely been ignored or distinguished away by a majority of the Court over the past four terms. In PLIVA v. Mensing, three Justices joined a portion of Justice Thomas's opinion that argued that the original meaning of the Supremacy Clause "suggests that federal law should be understood to impliedly repeal conflicting state law," a theory that would conflict with the presumption against preemption. Two years later, in Mutual Pharmaceutical v. Bartlett , a majority of the Court, while acknowledging that the preemptive scope of the federal law in question had posed "difficult ... questions" and "repeatedly vexed the Court," still found a state law unconstitutional without discussing the presumption against preemption. As a consequence, the presumption against preemption, formerly called one of the "cornerstones of ... pre-emption jurisprudence," appears to be no longer consistently applied, if not rejected, by the Court. With these principles in mind, there are two general categories of preemption: express preemption and implied preemption. The first way in which federal law can foreclose the operation of a state law is by express language in a congressional enactment, often called an express preemption clause. In those instances, determining the scope of the preemption clause is a matter of statutory construction. While the existence of an express preemption clause may imply a relatively straightforward resolution of whether a particular state law is preempted by federal law, express preemption cases can be as complex as implied preemption cases. For example, in a case called Cipollone v. Liggett Group, a very divided Supreme Court interpreted a provision in the Public Health Cigarette Smoking Act of 1969 that barred a state from imposing a "requirement or prohibition based on smoking or health ... with respect to advertising or promotion of any cigarettes." The Court issued three different opinions, none of which garnered a majority of the Justices, and ultimately concluded that the express provision in the 1969 law preempted state negligence and strict liability claims, but did not preempt claims for a breach of an express warranty. Nine years later, in Lorillard Tobacco Co. v. Reilly, a 5-4 ruling, the Court concluded that the same language from the Public Health Cigarette Smoking Act of 1969 preempted a state law banning outdoor cigarette advertising near schools. Together Cipollone and Lorillard illustrate that interpreting express preemption clauses in federal statutes can raise complicated and difficult questions for courts to resolve. A federal law can also preempt state law even in the absence of an express preemption clause. Courts have recognized two ways in which a federal law can implicitly displace a state law: field preemption and conflict preemption. The latter form of preemption may be further subdivided into impossibility preemption and obstacle preemption. The Court has struck down state laws when Congress has evidenced a desire to occupy the entire field of regulation, such that there is "no room for the states to supplement it." The classic example of a field preemption case is Rice v. Sante Fe Elevator Corp. , which held that states cannot regulate grain elevators licensed by the federal government because the implicit intent of the underlying federal scheme was to replace a system of dual regulation with a system of exclusive federal licensing. Other examples of where the doctrine of field preemption is implicated include state regulation of the construction of nuclear power plants, the registration of aliens, and foreign affairs. Finally, preemption can occur when a particular state law conflicts with federal law. A conflict exists most obviously when "compliance with both federal and state regulations is a physical impossibility." The quintessential example of impossibility preemption was provided by the Supreme Court in a case called Florida Lime & Avocado Growers v. Paul . Specifically, the Court, in providing a hypothetical example of what impossibility preemption would look like, stated that a federal law forbidding the picking and marketing of any avocado testing more than 7% oil would preempt for reasons of impossibility a state law excluding from the state any avocado measuring less than 8% oil content. Impossibility preemption has rarely been invoked by the Supreme Court, as impossibility has been described as a "demanding defense" when attempting to defeat the effect of a state law. Conflict preemption can also occur when a state law serves as an "obstacle to the accomplishment and execution of the full purposes and objectives of Congress." Obstacle preemption ultimately becomes a question regarding how much conflict is tolerable between the state and federal law. The answer to that question rests in the balancing of interests between the degree of impedance to the national purpose and the value of state autonomy in a given context. A clear example of obstacle preemption occurred in Nash v. Florida Industrial Commission, where the Court held that federal unfair labor practice laws preempted a state law denying unemployment benefits to employees that filed an unfair labor practice charge with the National Labor Relations Board. In Nash, the Court reasoned that the financial burden imposed by the state law impedes resorting to federal law as a means to stop an unfair labor practice. Obstacle preemption is perhaps the most difficult of the preemption doctrines to apply because of the "inherent uncertainty in determining Congress's intent to preempt based on an ex post judicial assessment of congressional objectives." While one might assume the existence of an express preemption clause in a statute eliminates the need for a court to examine whether a statute implicitly preempts a state law, the Supreme Court in Geier v. American Honda Motor Co. rejected such an assumption. In that case, Alexis Geier, after suffering severe injuries in a car crash, sued Honda, arguing that the car company had negligently and defectively designed the car without a driver's side airbag that might have protected her. Honda argued that Geier's claim was preempted by a federal motor vehicle safety regulation that allowed car companies the choice of installing an airbag, an automatic seatbelt, or some other passive restraint system. Justice Breyer, writing for a five-person majority, held that an express preemption clause in the Safety Act containing language that compliance with a federal motor vehicle safety standard did "not exempt any person from liability under the common law" excluded common law tort claims from the statute's preemptive reach. Nonetheless, the Court proceeded to explain that while the savings language removed "tort actions from the scope of the express pre-emption clause," it did not limit the operation of ordinary preemption principles, such as conflict preemption, because to do otherwise would allow states to "impose legal duties that would conflict directly with federal regulatory mandates."