I live in CA and never even looked into it. Got the jeep on 31s with stock flares, stuck out nicely, no problems. Went to 33 x 12.5 with tube fenders all around, haven't been hassled yet. I'm sure the law says it's a no-no, but cops don't really seem to pay attention to that stuff. They're more after rice rockets and such...
89 YJ 4.2L http://www.jeepforum.com/forum/f12/kgb-89-yj-storyline-build-thread-1520814/
96 XJ 4.0L http://www.jeepforum.com/forum/f177/600-96-xj-budget-daily-overland-build-1855418/