Where do you live that you can’t carry that baton?
http://www.my-self-defense.com/expandable-baton-laws.html
http://www.my-self-defense.com/expandable-baton-laws.html#californiajumpto
They consider it a “dangerous weapon” along the lines of a blackjack,billy or sap.
The revised codes are PENAL CODE
SECTION 22210-22295 which is a misdemeanor for possession and I could see it ratcheted up to felony assault depending on the circumstances it was used in. Ain't California law great./s This is definitely a risk in larger metro areas like LA or SF unless you take off immediately after using it. TTS (Tune em up, Take off and Shut up)
http://www.leginfo.ca.gov/cgi-bin/displaycode?section=pen&group=22001-23000&file=22210-22295