Veterans Medical Marijuana Safe Harbor Act This bill provides guidance related to veterans and medical marijuana that shall be effective for five years. Specifically, the bill authorizes (1) a veteran to use, possess, or transport medical marijuana in accordance with applicable state or Native American tribal law; (2) a Department of Veterans Affairs (VA) physician to discuss with a veteran the use of medical marijuana as a treatment if the physician is in a state or on tribal land that authorizes such treatment; or (3) a VA physician to recommend, complete forms for, or register veterans for participation in a medical marijuana treatment program in accordance with applicable state or tribal law. The bill requires the VA to report on (1) the effects of medical marijuana on veterans in pain; and (2) the relationship between state-approved medical marijuana treatment programs, program access, and opioid use and abuse reduction.