TexasCHLforum.com

Yep, believe it or not, Texas was a "retreat" state until about ten years ago. Didn't have to retreat inside of your home, but anywhere else it was a requirement if you could safely do so.

Generally, in order to claim self defense, one must be in a place where he has a legal right to be. For example, the bad guy who broke into your house can't shoot back when you shoot at him and claim self defense. He is a trespasser, so he loses that defense.
Obviously, if you illegally carry past a properly posted 30.06/30.07/51% sign you are not legally on the premises. You are a trespasser.
But what if no signs are posted, and a place is not otherwise legally prohibited, but you have an agreement not to carry there? For example, you belong to a club, group, etc., and your membership agreement says "no firearms." Since there is no sign properly posted, you carry concealed anyway, and no one knows.
Now, one day you have to use your gun in what would normally be justified self defense. Are you legally on the premises or not? There are no legal signs posted, but you have the agreement saying that you won't carry.
Not sure I know the answer to this one.