Here it is straight from the MCA, and based on this if he is going to carry inside city limits, get a IWB holster.
45-8-315. Definition. "Concealed weapon" means any weapon mentioned in 45-8-316 through 45-8-318 and 45-8-321 through 45-8-328 that is wholly or partially covered by the clothing or wearing apparel of the person carrying or bearing the weapon, except that for purposes of 45-8-321 through 45-8-328, concealed weapon means a handgun or a knife with a blade 4 or more inches in length that is wholly or partially covered by the clothing or wearing apparel of the person carrying or bearing the weapon.
45-8-317. Exceptions. (1) Section 45-8-316 does not apply to:
(a) any peace officer of the state of Montana or of another state who has the power to make arrests;
(b) any officer of the United States government authorized to carry a concealed weapon;
(c) a person in actual service as a member of the national guard;
(d) a person summoned to the aid of any of the persons named in subsections (1)(a) through (1)(c);
(e) a civil officer or the officer's deputy engaged in the discharge of official business;
(f) a probation and parole officer authorized to carry a firearm under 46-23-1002;
(g) a person issued a permit under 45-8-321 or a person with a permit recognized under 45-8-329;
(h) an agent of the department of justice or a criminal investigator in a county attorney's office;
(i) a person who is outside the official boundaries of a city or town or the confines of a logging, lumbering, mining, or railroad camp or who is lawfully engaged in hunting, fishing, trapping, camping, hiking, backpacking, farming, ranching, or other outdoor activity in which weapons are often carried for recreation or protection; or
(j) the carrying of arms on one's own premises or at one's home or place of business.
(2) With regard to a person issued a permit under 45-8-321, the provisions of 45-8-328 do not apply to this section.