I have lived in Tahoe for the past 30 years, I commute to the top of Donner Pass (those Damn Donners.....) every day, and was an active member of two of our local SAR teams, so I know a little about driving in CA snow. I bought chains before my first Tahoe winter and they have sat in the trunk/bed of my vehicle ever since, unused. When I got a new car, I would just transfer the chains from my old car, regardless of whether they fit my new tires. I always had good snow tires and AWD/4WD. Caltrans has asked me several times if I have chains with me and I say yes and they wave me through. I have never driven in R3 chain conditions (chains mandatory on all vehicles regardless of tire type or drive type), although I have heard about R3 conditions in certain areas during the worst storms. In general, Caltrans close the roads before they impose R3. The only exception I remember was during an unexpectedly bad storm when a bunch of tourons were trapped in Yosemite NP and Caltrans had to get them out of there because the Valley was running out of food. I think CA has particularly stringent chain regulations because the beaches are so close to the mountains and we can get so many tourons in the highlands who have never driven in or even seen snow before. YMMV.