I would be surprised if other schools don't scout like this as well. It is difficult to catch. Having caught it there should be punishment. But, perhaps the rule should be changed due to the impossibility of enforcement.
What do you suppose a coach will do if Michigan fans, or Northwestern fans, go to opponents' games and email the coaches with the other team's offensive signals? Are they going to delete the email, or are they going to print it, then delete it? After all, it's information in the public domain.