If you are on probation it is within a judge's discretion to allow you to use medical marijuana.
There is a difference between formal and summary probation - on summary or informal probation, you do not have to check in with a probation officer. However, you most likely signed a form that included a 4th waiver, which means the police can perform searches without a warrant.
Keep in mind, if the amount you possess is less than an ounce, it is an infraction that comes with a fine not to exceed, but will most likely be, $100. California Health & Safety Code Section 11357(b).
Answered on Apr 13th, 2013 at 1:07 AM