I learned about Princeton's Honor Code one cold, wintry night when I was a teaching assistant for a section of calculus, and the course instructor asked me to proctor an evening exam.
I use the word "proctor" for lack of a better word. I was told that I wasn't actually allowed to proctor the exam, or even be in the room where the test took place, since the Honor Code forbade it. The point of my being there was to answer any questions the students had. If a student found a typo or an ambiguous phrase in the test, I had to deal with it.
Princeton students came up with the Honor Code in 1893. The phrase the students had to write on their tests was: I pledge my honor as a gentleman that during this examination I have neither given nor received assistance, with the word "gentleman" remaining until Princeton went coed in 1969.
I distributed the exams, told the students where they could find me, and left.
The students came and went as they pleased. If they looked lost, I pointed them in the direction of the nearest restroom. I could hear voices in the exam room, but I wasn't permitted to do anything about it.
The atmosphere in the room seemed to get more boisterous as time went on. That seemed less surprising when I observed an empty six pack of beer being carried out after I collected the exams (by someone who was gentlemanly enough not to leave it there; the room was left in a newly acquired state of disarray).
Princeton was very proud of its Honor Code. Seeing it from the instructors' side, I'm not surprised that it was the students who demanded it. It's hard to imagine faculty coming up with a plan that would leave them outside in the snow while the students partied indoors.