i agree that you could possibly rig it with a carabiner. i have used this bag for the past 10 months while shooting overseas. note that it's small. my rebel t2i fills almost the whole main compartment. the one pocket in front holds extra battery and such. not much room for anything else. good bag if you don't need extra space.
there isn't an attached belt loop to this bag. I swapped out the original strap for a longer one to wear it cross-body, works well for me. And though it is a small bag, I think it would feel awkward attached to one's belt. That said, it is very sturdy and I think it would hold up to rigging it up with a carabiner.
No belt loop that can comfortably fit it to a belt, There is a loop that would make the bag dangle from your belt, if your belt was narrow enough to fit in that loop. And for a bulky bag (which is great to use if you use a shoulder strap) , hanging this bag on a belt would be getting it in my way - too cumbersome.