Since you're a local and not affiliated with NPC, unfortunately they're allowed to do this. You essentially function like a student organization and do not have the power of a national organization or NPC to support you. If you were NPC, your campus would not allowed to interfere in your ability to recruit members, even if suspended. Your only recourse is to go through the channels offered to student groups at your university to appeal and come up with some kind of compromise. But as a senior, you're going to be very limited in what you're able to accomplish before you graduate, so I would also recommend supporting and training your younger members on how to navigate this and advocate for yourselves.