OK, here's the reference, from the latest Captain's Club newsletter:
PREREGISTRATION. It's a must for your next true departure.
Soon, new government regulations will require that all cruise lines gather and submit key guest information prior to departure. To ensure that these requirements are met and that you enjoy a smooth boarding process on the day of departure, please visit celebrity.com, click on "Reservations/Guest Documentation," and complete the appropriate information prior to sailing. If you do not have access to the Internet [etc.]