The U.S. Supreme Court took up an appeal Tuesday from the U.S. Food and Drug Administration after a lower court found the agency introduced surprise requirements for applications to market new e-cigarette products.

The FDA has denied applications to market new e-cigarette products on the grounds that it’s unclear whether the number of adults who use them to quit smoking will outweigh the risk of young people taking up vaping. Below, the U.S. Court of Appeals for the Fifth Circuit held that the FDA had pulled a “surprise switcheroo” on e-cigarette applicants by requiring them to submit certain scientific studies to support their public health claims.