Cal. Business and Professions Code § 718

A physician and surgeon who is not licensed in this state but who is a commissioned officer on active duty in the medical corps of any branch of the armed forces of the United States may engage in the practice of medicine as part of a residency, fellowship, or clinical training program if all the following conditions are met: (a) The residency, fellowship, or clinical training program is conducted by a branch of the armed forces of the United States at a health facility on a federal reservation and limited in enrollment to military physicians on active duty in the medical corps of a branch of the armed forces of the United States. (b) The residency, fellowship, or clinical training program, as part of its program, contracts with or affiliates with a similar program in or at a health facility not on a federal reservation to offer specific courses or training not available at the facility located on the federal reservation. (c) The officers enrolled in the residency, fellowship, or clinical training program restrict their practice only to patients who are seen as part of their duties in the program. (d) The compensation received by the officers enrolled in the residency, fellowship, or clinical training program is limited to their regular pay and allowances as commissioned officers. (e) The officers enrolled in the training programs or portions of training programs not conducted on a federal reservation shall register with the Division of Licensing of the Medical Board of California on a form provided by the division.