Under current rules it is mandatory for him to be processed for separation based on drug abuse.
However, the separation authority can decide to give him one last chance and remain. That's going to be hard to do in today's environment. The Army is down-sizing, that means they are taking every opportunity to kick people out.
He should speak to the defense lawyers at TDS about this ASAP.
Concur with Attorney Cave.
I am licensed in the Commonwealth of Virginia, answering your query and my answer do not create an attorney-client relationship and I am not providing you legal advice. You should speak with an attorney to whom you have provided all the facts, before you take steps that may impact your legal rights--or rights to recovery of damages. I wish you the best of luck with your situation.