Big Frank, who says you can't detect at historic places in CA? I detect them all the time
If you talked to some select archies, they might try to tell you that md'ing is outlawed EVERYWHERE, but the truth of the matter is, unless you're snooping around some obvious historic monument, or being a nuisance, sticking out, etc... you'll be OK. Yeah, I probably wouldn't whip out the detector for the Shasta area ruins that sit right off the heavily trafficked road, if there were an archie convention going on at that exact moment next door. But for an old foundation out in the back-country, or more innocuous ruins at discreet times, I've never ran into a problem.
There also various levels of "government" land in CA. There's federally owned, state owned, county owned, and city owned. So it would depend on what level you're talking about. And even within those various levels, you sometimes have to dig real deep to try to find something that applies. And even when you think you've found something about "antiquities" or whatever, they would only apply to something older. Like, if you tell them you were only looking for modern change, or that "boyscout ring you just lost", those would be different matters. I guess it's kind of like picking your nose: If you ask someone if you can do it, they'll tell you "no".
If you don't wander around sensitive ruins at wrong times, making a mess, you'll be ok. Also, there's lots of private property (ranches, cow pastures, fallow row crops, etc...) that had old sites on them (stage stops, 1-room schools, old picnic spots, etc..) so the list is endless of where you can research out to hunt.
