Sambane - I'll give it a go:
Some states have allowed only modest range firearms for deer hunting, because of high human population density. Lots of small farms. Etc... So, to decrease the danger, decades ago those deer hunters were restricted to using shotguns, muzzle loading rifles, and archery gear.
Hunters knew this was sort of silly - and kept pushing to have rifles allowed. Eventually a compromise was reached, and rifles were allowed, but still not bottleneck cartridges. The various states still restricted the type of cartridge, to "straight wall cases" or similar wording. Rifles in 44 "magnum" or 38-55 or even 45/70 were legal, but not rifles in 30-06 for instance. This recently led to the introduction of a rifle cartridge intended to fill this niche market, the 350 Legend.
Since I live "out west" none of those restrictions apply to me, though others do. I am free to use anything, 6mm and larger, for whatever big game I pursue.
I think that more or less makes sense of it. :)