Compiled Laws, Chapter 750. Michigan Penal Code § 750.227a

Sec. 227a. Any person licensed in accordance with law to carry a pistol because he is engaged in the business of protecting the person or property of another, except peace officers of the United States, the state or any subdivision of the state railroad policemen appointed and commissioned under the provisions of Act No. 114 of the Public Acts of 1941, being sections 470.51 to 470.61 of the Compiled Laws of 1948 or those in the military service of the United States, who shall have a pistol in his possession while not actually engaged in the business of protecting the person or property of another, except in his dwelling house or on other land possessed by him, is guilty of a felony. This section shall not be construed to prohibit such person from carrying an unloaded pistol to or from his place of employment by the most direct route.