Limited endorsement that exempts its holder from the corridor rule; without it, crossing a border is lethal.
Phase One's rules confine entry into enemy territory to designated corridors, with free passage once inside, and this restriction does not apply to anyone holding the Scout endorsement. Team Retribution has only a limited number of scout spaces and all of them are already assigned.
That cap becomes urgent when Samantha stows away on the Party Planner without the endorsement. Carl explains that when the aircraft crosses the border she will literally tear a Samantha-sized hole in the plane, hurting Louis and everyone aboard and crashing them, and orders her ejected out the Bomb Bay rather than risk it.
The scarce permission that lets a unit cross a border outside the corridors without being torn out of place.