Or various municipal inspectors.
Some time back in my house hunting days, I was told that if there is no emergency egress, window escapes, or other avenues then the below grade basement could not be considered a living space. I never learned what my in-laws house built on a slope with the walk out basement was calculated at.
Everything varies by state, but a lot of walk-out basements will calculate that space as living space and the other side without the easy egress as not living space.