The license of any person whose permanent allegiance is due to the United States to practice pharmacy in the consular districts of the United States in China may be revoked by the consul if such person be found to have obtained such license by fraud, or be addicted to the use of any narcotic or stimulant, or to be suffering from physical or mental disease, in such manner and to such extent as to render it expedient that in the interests of the public his license be canceled; or to be of an immoral character; or if such person be convicted in any court of competent jurisdiction of any offense involving moral turpitude. It shall be the duty of the consul to investigate any case in which it is discovered by him or made to appear to his satisfaction that any license issued under the provisions of this chapter is revocable and shall, after full hearing, if in his judgment the facts warrant it, revoke such license.