Why does the legal definition of quackery vary among U.S. states?

In the United States, the definition of quackery varies from state to state because the legal authority to regulate health care and professional practice is reserved for individual states rather than the federal government.12

Under the U.S. Constitution, states retain direct power over health care, meaning that licensing requirements for medical professionals and the specific legal boundaries defining what constitutes the unauthorized practice of medicine are determined by state-level administrative agencies and licensing boards. Consequently, while federal laws like the Federal Food, Drug, and Cosmetic Act provide oversight for products in interstate commerce, individual states maintain their own discretion regarding the extent and nature of control they exert over medical practices and fraudulent claims within their borders.231

This decentralized approach means that what is legally permissible or classified as quackery can differ based on the specific statutes and regulatory limits established by each state's legislature.1