The U.S. Supreme Court grappled on Monday with the U.S. Food and Drug Administration's defense of the agency's refusal to let two e-cigarette companies sell nicotine-containing flavored vape products that regulators found to pose a significant health risk to youths.

The Supreme Court on Monday heard arguments about the federal regulation of flavored e-cigarettes, in a case pitting the Food and Drug Administration (FDA) against two vaping companies. Justices weighed whether the agency acted lawfully when it denied the applications of the companies to market fruity and dessert-flavored liquids for their electronic nicotine products.