It has always been legal here and I've been quitr happily and safely doing it without incident since 1970 or thereabouts.
In fact the only danger presented has been from jealous or pissed off cagers who will occasionally try to close the gap.
Cali has recently begun an ad campaign informing the general herd that the practice is legal and reminding the cagers of their role in keeping it safe.
The study was actually ordered by those seeking to abolish lane splitting. I think the facts kinda wrecked their day. But in combination with environmental and traffic concerns we don't expect they will try to contest it again for a very long time.