I am using devise to manage user authentication in my rails app. Devise is really great for that.
However I have a special requirement for my application: A user mus
I would just use model validation. I'm assuming your User class has the devise method
class User < ActiveRecord::Base
devise :database_authenticatable, :registerable #etc
before_validation :whitelisted
def whitelisted
unless celebrityemail.include? email
errors.add :email, "#{email} is not on our invitation list"
end
end
end