The police did declare a riot and Liefwalker was apparently present as violent acts were committed, including projectiles being thrown at police. However, the charge does not indicate that he was personally involved in a violent act. It is also not clear that he was a participant in the protest as opposed to being present at the scene as an observer. This is the type of charge that comes with the refusal to heed warnings to disperse. As such, it is technically a criminal act but it is closer to a non-violent form of civil disobedience.
We have often discussed how free speech is being curtailed by universities by disciplining students and faculty members for their speech outside of schools, particularly on social media. I would include demonstrations in such exercise of free speech.
Some 23 people were arrested, including some for “unlawful assembly.” Assuming that Liefwalker does not face a charge of violence, I would strongly encourage the school to treat this as a matter outside of the scope of university review or action.