The National Guild of Hypnotists is a great resource for everything related to hypnosis. Here is their list of regulated and non-regulated states.
20 states have no regulation that affects hypnosis:
Alabama, Delaware, Georgia, Indiana, Iowa, Kansas, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Nebraska, North Dakota, Oklahoma, Oregon, Pennsylvania, South Dakota, Vermont, Virginia, and Wisconsin.
15 states (plus District of Columbia and Ontario) accept NGH regulations:
Alaska, Arkansas, Arizona, District of Columbia, Hawaii, Maryland, Mississippi, Missouri, Montana, New York, Ohio, South Carolina, Tennessee, Texas, West Virginia, Wyoming and Ontario.
15 states have explicit laws regulating practice of hypnosis:
California, Colorado, Connecticut, Florida, Idaho, Illinois, Minnesota, New Jersey, New Hampshire (regulation voluntary, otherwise Guild Standard), New Mexico, Nevada, North Carolina, Rhode Island, Utah, and Washington.