He can ask the supervising officer, and can (if appropriate) try to appeal. But if he goes without the permission of the probation department then he'll be in violation of the probation conditions.
If it's truly important to go, hire a local attorney to help you.
Either notify the probation department or have your case called up in front of the judge and seek permission to attend the funeral. Notifying them as to where it is and what time and if you'll be going somewhere else after the funeral for a family get together.