If they are indeed going to explore the origins of General Order 7 on Discovery, then what happens on Talos 4 must be really horrific for the "enlightened" Federation to threaten the death penalty.
On further examination, whatever happens must be horrific to humans. The text of General Order 7: "The following officers have visited Talos IV and recommend that no human should ever visit it again".
Who's an expendable human character on the show? (Number One, you'd better go hide...) Does this mean an alien like Saru will survive whatever horror awaits on Talos IV?
EDIT: On second glance, the general order is inconsistent. It says no human may visit in one place, and no one may visit in another.