A dispute over the U.S. Food and Drug Administration's refusal to let two e-cigarette companies sell flavored vape products due to their health risk to youths goes before the U.S. Supreme Court on Monday in another case involving the power of regulatory agencies.

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.

The FDA has rejected applications for more than 1 million fruit, candy and dessert-flavored e-cigarettes and vaping liquids in recent years.