How can someone get off probation (for a DUI in California) early?

Someone I know was put on probation for 3 years. They've complete all the court ordered things, like paying the fine, community service etc. 2 years later, and 1 year left into the "probation" period, how do they request to get the remaining time dropped? They've moved about 4 hours away from where the initial accident took place and was able to complete their court ordered things where they live now. They did have to go BACK to where the accident happened in order to pay the fine and all the court mandated stuff. Who would they contact in order to drop the probation? Would they have to go back to the original courthouse or can they do it where they live now?