When you go to the gate, your U-Card would get scanned. If you drop your classes then you are no longer a student at the U. This would show up at the gate and I believe you would not get admitted to the event.
I just called the Gopher ticket office and the girl told me the U hasn't officially decided what, if anything, will be done at the gates of the stadium to assure that those entering the stadium are the same students who purchased the tickets. The way I see it, there are a few scenarios:
(1) A system is arranged where a students U Card is scanned, remotely somehow or with something that's set up on-site, during the normal frisking to enter the stadium. The ticket doesn't have a name on it or anything like this - it's enough to have a ticket and a U Card that can be scanned to assure you're a U of M student. The only way I can see the U scanning every ID is if there's a set up at the security checkpoint for frisking. If you make the line stop a second time for scanning, getting into the stadium is going to be very, very slow.
(2) A system is arranged like hockey season tickets, where your name is printed on your ticket. You flash the ticket and the U Card at some point, and if the names match, you're golden. If the names don't, you have to go through a separate line and have your card scanned.
(3) There are no names printed on the tickets, and no one is scanning IDs. When entering the stadium, it's enough to have a U Card that is (or appears to be) you and the ticket. Flash the ID on your way in, and you're all set.
(4) There is no name on the ticket, no ID required. Basically, if you have a ticket for the game that says you sit in the student section, you're getting in and sitting in the student section.
#2 and #3 seem the most likely to me, with #2 probably being the most likely since there's a example of how this works with hockey games. Then again, #2 worked at the beginning of the hockey season, but as ushers started to care less about arguing with students, they started just letting everyone in and it sort of defeated the purpose. #1, though it would be the most effective at assuring everyone entering the gates as a student is a student, would be a major hassle and slow down entering the stadium to a crawl. #4 seems unlikely, because why would you go through the hoops of this new ordering system and then not back it up with anything at the gate?