Defend Adult Son Against Conviction Related Removal

My 22 year old son has his green card. It appears that he was arrested for possession of marijuana last year. I did not know of this or I would not have taken him with me on our vacation. I watched in horror as he was led off by immigration officers and given a document to appear in Immigration Court to defend himself against being removed from the United States. I almost fainted, and I have not been able to sleep or eat (although when I peep into his room at night, he is sleeping like a baby and his appetite does not appear to be affected). As his parent, I am very concerned and worried. Is there any relief for me?
If he was found guilty of the marijuana charge, it is possible that your son could qualify for a Cancellation of Removal or a stand-alone 212(h) Eligibility Waiver.