WE've been complaining for some time now about the fact that the campgrounds we visit are often fully reserved, and yet there are always quite a few open sites. Clearly, people are making campground reservations (sometimes at multiple locations) and then not showing up--and not bothering to cancel them.
Well, there it s new law in town https://www.sfgate.com/california-parks/article/california-law-harsher-penalty-campsite-no-show-18418167.php
Best news is that if you fail to use a campsite and fail to notify them about it, you won't be allowed to make future reservations until you resolve the issue. This should help!