Okay, we have been over this like 1001 times.
The correct term for what you are talking about is LANE SHARING. There is a difference between splitting and sharing.
All states that I am aware of that have a law prohibiting this act title it (and describe it) as lane sharing. We are lucky that in CA, we do not have a law prohibiting lane sharing.
If you are sharing the lane with one of the vehicles and doing so safely, it is legal in CA in illegal in states such as Hawaii and Washington. If you are straddling the lanes in the process (not entirely within one lane), it is illegal in CA as lane straddling is specifically prohibited by the CVC as it is in most all states and countries.
You will not find "lane splitting" addressed in CA law. Just straddling.
Unfortunately, many cops confuse splitting with straddling and I think most riders don't understand the technical difference between lane sharing, lane straddling and lane splitting. If people would stop calling the act "lane splitting" and started consistently calling it "lane sharing," it may cut down on the confusion.
The important thing to understand is that there is a law in CA prohibiting straddling lanes (21658(a) CVC). There is no law specifically allowing or prohibiting lane sharing in CA. If you are cited, it will likely be for lane straddling, unsafe lane change, unsafe passing, speeding or maybe reckless driving. The officer would need to settle on whatever violation s/he felt was most appropriate, based upon what s/he observed.
For reference:
CVC 21658. Whenever any roadway has been divided into two or more clearly marked lanes for traffic in one direction, the following rules apply:
(a) A vehicle shall be driven as nearly as practical entirely within a single lane and shall not be moved from the lane until such movement can be made with reasonable safety.
(b) Official signs may be erected directing slow-moving traffic to use a designated lane or allocating specified lanes to traffic moving in the same direction, and drivers of vehicles shall obey the directions of the traffic device.