I'm going to take the other side of this argument. Take away the facts that the road accesses a nice beach and that we're talking about a rich guy (who is obviously super-evil because he is rich).
A bunch of people are mad because a guy closed a road that belongs to him.
The fact that the road had previously been open at all is only because someone was nice enough to keep it opened. So the current owner wants to be a jerk and close the road. It's his road and unfortunately, there's no law against being a jerk. if the Coastal Commission insists there should be public access to all CA beach property, let them pay for an alternate way to access the beach. They should have considered that this private road could be closed at any time and been proactive. Using eminent domain to force the owner to open the road bothers me. Letting the government have that kind of power can easily backfire.
In Pacifica where I live there is a trail called Boyscout that sits almost totally on private land. A new owner purchased the land about 12 years ago and was OK with the trail, provided that anyone riding the trail sign a waiver, (I'm not sure the waiver is enforced too much anymore) Let's pretend it was one of the best trails around and became famous worldwide. What if the land got sold and the new owner put a fence around his property and closed public access? That would be too bad, but that would be within the rights of the new owner. I see no difference in the Martin's beach situation.
Within California there are some interesting laws and civil legal precedents that affect access on roads/trails such as this. It boils down to this: If there is an access-way that the public has used to cross private property for a certain amount of time to travel between two public accessible locations a right-of-access has been established. The time period is determined by similar cases in the jurisdiction where any case is brought to court. Cases in other jurisdictions can be used for reference if there is no similar legal challenge in the jurisdiction.
This is a bit different than the eminent domain process. It is something that occurs all the time across the state, and property owners can't do anything about it if the court orders public access other than push an appeal...which most higher courts end up considering a waste of their time and refuse to rule on it.
This is for public access in all areas of California, not just the coast, but when you add that to the way coastal access is legally protected in California, beach access roads end up being something private property owners never get to control. Doesn't mean they don't try to stop the public using creative, and sometimes illegal, ways.
This kind of thing isn't just a California thing, I understand that access rights in other states can get just as hot. As a way to get back at the property owners, some people have published books and webpages that list access-ways to the coast. I have seen such books for the greater Los Angeles/Orange County/San Diego areas and for Oahu in Hawaii.
