Heather Kokesch Del Castillo launched a dietary advice business in Monterey, Calif., in 2014. Ms. Del Castillo eventually established a nationwide client base as a health coach." But when her husband, who is in the Air Force, was transferred to a base in Florida, her business hit a roadblock. A Florida Department of Health investigator showed up ... with a cease-and-desist letter and a $750 fine. After nearly two years of operating her business in Florida, Ms. Del Castillo learned that she had run afoul of a law requiring any person offering dietary advice to possess a state-issued license. Qualifying for that permit requires a bachelor's degree in dietetics, a 900-hour internship, a passing grade on an exam administered by the state Commission on Dietetic Registration, and a $355 fee. A licensed dietitian had tipped off the Health Department that Ms. Del Castillo was giving unauthorized advice. She retained the Institute for Justice, a public-interest law firm, to fight the law that stripped her of her livelihood. About 1 in 4 Americans need licenses to perform their occupations. In some states, florists, taxidermists and even fortune-tellers need licenses to operate. Far too often, these licenses serve less as safeguards of public health and safety than as barriers to entry. In many cases, the state-appointed boards that issue licenses are stocked with industry insiders seeking to restrict competition. Aggressive licensing regimes limit the ability of Americans to move from state to state. All Americans ought to have access to license portability.