[EricH]

Originally Posted by Cory

I didn't mean to say that exclusively, because they're on a team at the event, they cannot volunteer, because of impartiality, or any other reasons, but rather that if you are a technical mentor for a team, the team will probably need your help throughout the competition, which would rule out the possibility of refereeing.

Depends on the team. 330 has a reliable bot, so we can spare mentors unless something really big breaks, but for other teams, say 1697 (Gyros, who were a rookie at LA and had a robot that kept breaking or not being ready), mentors may be in short supply.
If a team has a lot of students and help is needed, the team can spare the students if they are needed. I spent Houston nationals resetting Galileo and two teammates filled in (at least on Thursday) to do the same thing on Newton. We only had 14 students total on the team.