I know with my fraternity once you pledge us you cannot pledge another fraternity

If a pledge isn't even an initiated member of your fraternity yet, how can your fraternity dictate what he does after he depledges and cuts ties with your organization?

I'm just guessing here but I believe he means initiate. Or perhaps it is campus protocol that the chapters on his campus do not rush former pledges of other fraternities.

Also, some NICs do not allow a member to withdraw (terminate membership) on their own accord without jumping though a lot of hoops. As such, to be able to join another fraternity, a rushee needs a written confirmation from the former NIC HQ that he is no longer a member. If he doesn't have that, and the campus knows he was initiated in another fraternity, then they won't pledge him.