The process is very simple. Several hours before the scheduled park closing, resort guests can pick-up a wristband at one of several locations throughout the EMH park. That wristband must be shown before the guest will be permitted to board any attraction during the EMH hours.
They will not "shoo" out people who are non-resort guests--but they will not be able to board any of the attractions.
IMO, these night hours are a fantastic idea. We've never used the morning hours because, frankly, setting my alarm for 6:30am so that I can race to a theme park isn't my idea of a vacation.
Using a split system of some morning hours and some night hours is a great solution that satisfies everyone.