1. State of principal license. A physician must designate a member state as the state of principal license for purposes of registration for expedited licensure through the compact if the physician possesses a full and unrestricted license to practice medicine in that state, and the state is:
A. The state of primary residence for the physician;
B. The state where at least 25% of the physician's practice of medicine occurs;
C. The location of the physician's employer; or
D. If no state qualifies under paragraphs A to C, the state designated as the physician's state of residence for the purpose of federal income tax.
2. Redesignation. A physician may designate another member state as the state of principal license at any time after a designation under subsection 1, as long as the state meets the requirements in subsection 1.
3. Rules. The interstate commission is authorized to adopt rules pursuant to section 18516 to facilitate designation pursuant to subsection 2 of another member state as the state of principal license.