Freedom of religion and speech are being violated. Honestly if this is happening, you could take this to court. Especially if they don't allow you to. You have a right to expression of your religion! There is no argument for yes to this one... Unless wearing a feather offends someone.
It would only be fair if EVERYONE had to get permission to wear things ethnic or religious. And since it would obviously be ridiculous to make a student get permission to wear a cross or a claddagh ring, the same thing goes for feathers. Requiring permission would be racist, demeaning and discriminatory.