On Friday, a German consul sent a letter to Governor Steve Bullock, saying their government could investigate and prosecute Kaarma under German law.
A University of Montana professor said German gun owners use firearms for hunting and shooting sports, much like in Montana, but guns are almost never for self-defense.
"Some people here feel safe because they have a gun because they feel they can personally protect themselves, Germans feel safe because barely anybody has a gun," said Henriette Lowisch, an Associate Professor at the School of Journalism at the University of Montana.
Lowisch said in her home country of Germany, a gun culture does exist, but it involves law enforcement, hunting and shooting sports almost exclusively.
"Nobody carries or is allowed to carry a gun for self-defense," she added.
Lowisch said it's also a multi-step permit process to purchase and own a firearm and ammunition.
"First of all you have to explain why you want that gun, what you want it for, why do you think you need it," Lowisch explained.
German gun purchasers also have to pass a background check.
"You know, you have to be able to show that you're able to handle a gun safely, that you have a safe place to put it."
It's a much less restrictive process in Montana. The National Rifle Association website shows under state law, a person does not need a permit to buy or possess a gun, but a permit is required to carry a concealed handgun.
"It also is somewhat, a little bit scary maybe in the beginning to imagine that somebody else that you encounter on the street might have a gun," Lowisch said.
And Montana citizens can own machine guns-- weapons Lowisch said are classified as "weapons of war" in Germany.
"Nobody is supposed to own them except the military," Lowisch explained.