I'm a student at a much smaller university than Stanford. I can tell you with confidence your statement of students not leaving campus once they move in cannot work. For one, consider the students who live in off-campus apartments. How are they going to get food? At my school, meal plans cost a crapton of money, and it's a lot cheaper to just buy groceries and cook for yourself.

Even if you forbade those students from coming to campus, how would you prevent students from leaving? Barricade them in? Our shortened fall break heavily encouraged students to stay on campus, but so many people left to see their families. It's not realistic.