Order of Protection

Minnesota- An OoP was issued against my son by his ex girlfriend in Feb. There was no violence or threat of, she just wanted him to quit "bugging" her. (her words in court)She wanted him removed from the college they both attended which did not happen at that time. He has not had any contact with her at all since that day although he does see her in one class but stays as far away as possible. My son just received a notice to appear in court for an alledged violation of the OoP. Someone he vaguely knew spoke to the ex girlfriend at school about him, which he had no knowledge of and she filed charges against him. He has been suspended from school, and may lose his eligibility in the National Guard because of these charges. He has never been arrested, so it's just her word. Should we get a lawyer for him? What are his legal rights as this is totally unsubstantiated and has the potential to ruin his life and any hope of doing what he would like in the future, such as a military career? Is she legally liable if it can be proven that this is malicious on her part? Sorry this is so long, I am very scared and frustrated. Thank You!
He has also lost all his tuition for this quarter at school.