Except for the city of San Diego, kratom is 100% legal in the state of California. In 2016, the San Diego city council decided to ban kratom within city limits. This does not cover all of San Diego County, however. It only reaches within the city limits.
That being said, the rest of California, for right now, accepts kratom as legal, so if you are in the San Jose area, you are able to use kratom without worrying about breaking any laws. It has been thought that the DEA wants to ban the use of kratom, but they have yet to be able to do so.
They originally cited it as an “imminent hazard to public safety”. But the public has a lot to say about this. The idea to ban the substance was delayed, giving the public time to comment, and the DEA has since changed their opinions, at least of how dangerous kratom is to the public safety. So for now, kratom is completely legal in most areas, including San Jose.