The U.S. Supreme Court on Monday heard oral arguments in the case FDA v. Wages and White Lion Investments LLC, dba Triton Distribution, a case concerning whether the Food and Drug Administration (FDA) acted properly of barring two makers of flavored liquid for e-cigarettes from marketing their products.

The Supreme Court on Monday pressed the Food and Drug Administration on whether it followed the law in its effort to keep flavored e-cigarettes off shelves, weighing a lawsuit from a multibillion-dollar industry that has come under scrutiny because its products are popular with school-aged children.

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