In reply to Manos de Piedra: I'm not in the CC Committee so this is just a personal view.
The land is private property - the same as your or anyone else's house, garden or driveway. I can assume you'd get rather annoyed if your neighbours parked on your driveway without asking, therefore the same applies here. It's bad manners, and as with annoying a neighbour they'll probably think you're a prat, give you some harsh words but won't be in a position to clamp you.
However, as with the hypothetical situation of someone parking on your driveway there is big difference between someone doing that all the time meaning you can't park your own car and them doing it once when there is loads of space and it doesn't interfere. In your case it's just a mild case of bad manners rather than causing a major nuisance. Unfortunately it doesn't take much to go from one person parking there to having twenty cars.
However, in this case I'd say that it's mainly the CC's fault for not replacing the electronic lock on the barrier after it broke ages ago. If we fixed that then this just wouldn't be an issue. We'd have to be extremely naive to think that a sign and an unlocked barrier is going to stop anyone from parking there indefinitely given the possible alternative of them having to park over a mile away.
Therefore, don't be surprised if you try and drive in to find the barrier locked again in the near future.