First, Lethbridge isn't like Calgary, Toronto, or Vancouver. Airsoft isn't really as established there. You have to drive out a few hours in order to play if you don't want to go to Coulee Runners (one of the places I'm thinking of you have to be introduced/vetted for).
Second, IF and only IF the farm is VERY secluded (ie. 10+ acres and a buffer zone that's fenced/treed where no one can see you or will EVER pass by) AND OUTSIDE CITY LIMITS (and I don't mean Coalhurst, Coaldale, etc. I mean properly outside city limits, in the sticks where there aren't any such bylaws like below).
Read this: (Section 15, subsections a to e):
Looking at Schedule A it's going to be a $500 fine AND the police will take all your stuff.