You state that the Judge ordered random screens. I am going to assume that the Judge ordered you to remain drug (and possibly alcohol) free. Your medical marijuana license does not permit you to violate your probation. So if the Judge ordered your to remain drug free then you cannot use marijhuana, notwithstanding the fact that you have a license to use it. It would be similar to a judge ordering someone who has a driver's license not to drive as a condition of probation. If you want to use marijhuana and you have a valid license to use it, you can go back to the Judge and ask the Judge to modify your probation to allow you to use marijhuana.
Robert D. Lewin, Attorney
LEWIN & LEWIN, CRIMINAL LAWYERS
Offices in Malden, MA and Andover, MA serving all of Eastern, MA
Don't risk it, do as Attorney Lewin suggest.
This is not intended as legal advice and does not create an attorney-client relationship.