I would petition to have letters of guardianship (in MA) as soon as possible. If you need to move him before such a petition can be heard, your son's level of impairment will direct how this goes. In some jurisdictions, the court appoints an attorney from their volunteer panel. If your son can express a desire to move to MA, the court-appointed attorney can then recommend the move while you file a noticed petition to fix his residence out of the state. This way, he can move immediately and you will retain your powers as his fiduciary. Otherwise, you can petition to terminate the proceeding, effective upon issuance of letters in MA. First, I would call the probate clerk in the County you want to move to and ask if the CO proceeding has to be terminated before the MA court will hear your petition (this is the case in Maine). I hope this helps!