Here is the text of the email, it's dated 17 April on the usfirst.org page
New this year! Attendee Registration: FIRST is requiring that all Championship attendees (students, mentors, spectators, etc.) register for the Championship event. Attendee registration grants participants access to activities and event transportation. We encourage you to register your team members in advance to save time when you arrive on-site at the Championship. You can complete attendee registration here:
http://registration.experientevent.c...aultTeams.aspx