I personally dislike the use of shot for big game, but it seems that some jurisdictions have decided that it is in the interest of public safety to mandate it. Lets consider the advise given by some that the range be limited so that all the pellets strike within a 30" circle. IMHO, a shot pattern that strikes with at least some pellets on the periphery of a 30" circle means that those outside pellets will be ineffective with respect to the wounds they inflict, if they even hit the deer. The heavier the shot, the fewer pellets there are to put on target, so you don't want any pellets to be out of the kill zone. For buckshot to be most effective, all the pellets must strike the kill zone, so an 18"-20" pattern is a better measure on a broadside animal, such a shot would cut off the top of the heart, shred the lungs, and possibly damage the spine. If one uses buffered shot from an open choke, this limits the range to the target to about 25 yards. If the animal is facing directly towards or directly away from the hunter, the pattern should be reduced to 12" or a range of about 15 yards. Get ye to a tree stand!
If it was me living in BC, I'd just hunt in an area that allowed an appropriate big game firearm.