Vong said the practice poses no health risks, prompted no complaints from clients and that the treatments, which cost $30 for 20 minutes, were popular and profitable. "There is not a single instance of harm attributable to fish spas in the entire world," said Clint Bolick, a lawyer for the libertarian-leaning Goldwater Institute, who is pressing Vong's case in court.

Fish pedicures are popular in Asia and spread to some U.S. cities in recent years. But Texas, Washington, Massachusetts and New Hampshire have outlawed the practice because of health concerns.