The United States Supreme Court case, UNITED STATES v. AN ARTICLE OF DRUG . . . BACTO-UNIDISK, in 1968 revolved around the classification of a product as a drug under the Federal Food, Drug and Cosmetic Act (FDCA). The product in question was Bacto-Unidisk which was used by laboratories to determine antibiotic susceptibility of bacteria. The government argued that it should be classified as a drug because its intended use had an impact on human health. However, the manufacturer contended that since it did not directly interact with humans or animals but only tested bacterial sensitivity to antibiotics, it could not be considered a drug. The court ruled in favor of the government stating that any substance intended for use in diagnosis and treatment can fall within FDCA's definition of drugs even if they do not have direct application on body.

In the dissenting opinion for UNITED STATES v. AN ARTICLE OF DRUG . . . BACTO-UNIDISK, Justice Fortas argued that the majority's interpretation of "drug" was overly broad and not in line with congressional intent. He contended that Congress intended to regulate products used directly by consumers or physicians for treatment of diseases, not laboratory supplies like Bacto-Unidisk which are used indirectly in diagnosis. The justice also expressed concern about potential overreach by the Food and Drug Administration (FDA), cautioning against giving it unchecked power to regulate a vast array of substances without clear statutory authority from Congress. He believed this could lead to arbitrary enforcement actions and stifle innovation in medical research due to regulatory uncertainty.