The issue hinges on whether he's a Montana resident. You can be a resident of more than one state (say, if you have a second house), but the intention must be to live in that state as a resident. A temporary work assignment, with a known termination date, won't qualify. It has to be at least open-ended.
Horsehockey.
College students are a great example:
https://www.atf.gov/firearms/docs/r...residency-out-state-college-students/download
ATF Rul. 80-21
[Status of ruling: Active]
The Bureau has been asked to determine the State of residence of out-of-State college students
for purposes of the Gun Control Act of 1968. “State of residence” is defined by regulation in 27
C.F.R. 178.11 as the State in which an individual regularly resides or maintains a home. The
regulation also provides an example of an individual who maintains a home in State X and a
home in State Y. The individual regularly resides in State X except for the summer months and
in State Y for the summer months of the year. The regulation states that during the time the
individual actually resides in State X he is a resident of State X, and during the time he actually
resides in State Y he is a resident of State Y.
Applying the above example to out-of- State college students it is held, that during the time the
students actually reside in a college dormitory or at an off-campus location they are considered
residents of the State where the dormitory or off-campus home is located. During the time out
of-State college students actually reside in their home State they are considered residents of their
home State.
