Actually there's a place near us (Bath, OH too bad it's about a 2 hr drive from C-bus!) that has never restricted people based on the equipment. They probably SHOULD, but they haven't because I've seen a ton of people go to their schooling days sans vest. But maybe they just really want that $25/person from them ;) It's certainly not a good idea to school xc without your vest, those jumps are NOT forgiving!
"The times when you have seen only one set of footprints in the sand, is when I carried you..."