Back in 2008, before he even began his career at Iowa, Riley Reiff was arrested for an unusual off-field incident. I'll let Black Heart Gold Pants, SB Nation's Iowa blog, summarize what exactly happened.
Reiff was involved in a small but hilarious run-in with the police when he was eighteen. Reportedly, he was found by police officers in some state of undress in downtown Iowa City -- if you've never been to Iowa City while eighteen years old, this is not an uncommon occurrence -- and led said police officers on a chase through downtown, eventually knocking over some trays at a late-night pita shop just for good measure. It's nothing; he was a kid (not even enrolled in college yet), he made a mistake, he never did anything untoward again, and he eventually became a team leader of some renown.
According to a report from ESPN on the incident, Reiff allegedly led "at least eight Iowa city police officers on a 20-minute foot chase." He ended up being charged with misdemeanor public intoxication and interference with official acts. He pleaded guilty to both charges.
On the off-field incident his freshman year at Iowa: "It was a learning experience; it was before I was a freshman in college. It was a really embarrassing incident and I've moved on. I've been a great citizen ever since and I've put it behind me."
Lions head coach Jim Schwartz was also asked about the incident.
On Reiff's off-field incident as a freshman: "We felt very comfortable with his explanation. That was right when he went onto campus as a true freshman, something that's long in his past and he hasn't had anything since. I think we've all done some things when we were freshmen in college that we didn't want coming back on us. I think the thing that gave us a lot of comfort was the fact that it was an isolated incident, there really hasn't been anything else. He's been incredibly productive and he's been a model citizen for Iowa and that gave us a lot more ease with that."
Basically, Reiff made a dumb mistake four years ago and hasn't done anything like that off the field since. It's obviously not smart to run from the cops and be excessively drunk in public, but I don't see this as a very big issue at this point in time.