DENVER  For more than a decade, Mark Cooper has had a bustling naturopathy practice in Colorado Springs, treating everything from chronic headaches to digestive problems to insomnia.

Mr. Cooper has a license in Montana to practice naturopathy, which uses natural herbs and remedies to treat medical conditions and which concentrates on dietary and lifestyle habits. But in Colorado he is unable to get a license because no regulatory system for naturopaths exists.

“The whole issue is fear-based ignorance,” said Mr. Cooper, who sits on the board of the Colorado Association of Naturopathic Doctors, which has proposed a bill this year that would allow naturopaths to get licenses and create training and treatment requirements for practitioners.

“Once somebody fully understands what our medical training is and what we actually do, they look at us and say, ‘Oh, my gosh, I didn’t realize that,’ ” he said.