Legal Question in Real Estate Law in California

Of course. It's no different than being refused entry into my house just because you want in.

Yes, it's legal. The security people were put there by the community's management, duly elected and hired by the owners, to do exactly what they did. If you leave home without a key, you'll be barred from entry by your own door; if you leave without your ID, you'll be barred from entry by the security people you have (by inference, at least) selected, hired, trained and instructed.

You either agreed in writing [CC&R's] or by actions in the community being gated and identification having to be shown, so you can not complain that security follows the rules.