I agree that it would be unfair to have to retroactively prove you were in place, but there are likely many situations where the company will have you dead to rights. What if the pilots in question were on SC until 0100, they were called at 2300 to fly, and the company has a record of them jump seating out of their assigned base on a 4 hour flight leaving at 2200? DAL doesn't seem like a 1 bad decision company, what if after a pilot missed an assignment the company went back and realized that for the past 10 years they've been cutting out of short call early without getting permission from CS. That would be indisputable evidence documenting systemic abuse of the system. I'm sure there are more situations similar to this one.