Once you are a RESIDENT of a US state, you may own and possess guns. Which state you reside in will determine your ability to carry such guns in public. Some states will not issue carry permits (if required) unless you are also a US citizen. Nevada is not one of them, but Oklahoma recently changed their law to require it. A Montana expert will hopefully chime in soon. I have family in Montana, but am not up there nearly often enough to have looked into all the laws.