Well, having pot or drug paraphernalia is a crime, fighting can be a crime, and underage drinking is a crime, so I would say yes, these definitely can lead to being kicked off the team permanently.
So are speeding and not wearing a seatbelt
Those are two totally different sets of crimes, and if the whole incident with Ndamukong Suh a few years ago was any sort of indicator, Bo Pelini has much more lax standards on that than the ones that have supposedly been perpetrated recently. Bo has a zero tolerance policy for underage drinking and (I would imagine) any sort of illicit drugs.
Even when Quinten Castille got kicked off the team a few years back by Bo for smoking weed, it was something like Castille's 3rd strike.
This is what I remember.