What you think it means: I don’t know about you, but if I hear that an animal has been raised and killed in a certifiably humane way, I think that means it has been fed food food that is not animal by-product, and had access to ample outdoor space, as well as freedom to engage in natural behaviors (foraging, eating grass, etc).
What It Actually Means: Hold on to your hats for this doozy — Humane is actually a completely subjective term. Finding reliable info on this was tough, and what I was able to dig up was for chickens. The “Certified Humane” label does not require any outdoor access for laying or broiler chickens. It does mean that chickens were not subjected to tiny cages, but doesn’t they were not overcrowded (certified humane farms must only be provide with 1-1 ½ square feet of space per hen). Also, beak trimming, performed to prevent a chicken from picking its too-close neighbor, is still allowed.
Takeaway: The Certified Humane label does mean that some considerations for the chicken’s well being were taken into account, but it doesn’t even come close to providing the guarantees the label would seem to suggest. The fact that it was difficult to find, clear, concise, reliable info on this was a major bummer for me.