While I am not familiar with his particular case, a probation usually comes with a restriction of travel. He needs to talk to his probation officer about getting a permission to travel for legitimate reason.
For example, if his conviction resulted in him being expelled from the school, his F1 visa would be invalid and he has no legal status to stay in US. That would be a valid reason.
Remember the state court and the immigration are different level of governments and they don't talk to each other.