It's funny because I've often thought about using .223 for whitetail deer.
I've heard it has good result with good shot placement (that is the key to any ethical kill with any cartridge).
I don't have a desire or purpose to use a .223 since I have other calibers in hunting setups ready to go.
I get a little skeptical with larger game like elk, moose, bear, but it seems that, again, with proper shot placement, a cartridge with good ability to penetrate can take almost any size game.
I think the biggest question is not whether you can, but whether you should - ethically.