Correct me if I'm wrong, but doesn't AL have a similar law only it pertains to ones yard or land?
I don't believe any state allows deadly force for the protection of personal or real property.
The caveat to this is that many states allow you to use deadly force if you're in your home or place of business, some states allow you to use deadly force in your home or place of business only if you reasonably believe that the person is committing or intends to commit a felony, some states allow you to use deadly force in public ("stand your ground") if you believe the person is committing or intends to commit a forcible felony, etc.
So, if someone is stealing property from your house or land, and the commission of that crime constitutes a felony, you can often (depending upon the state and its specific laws) use deadly force and claim self defense...
but it's not directly related to defense of your property. It's related to the likelihood of harm to the person during the course of a felony being committed, or during the course of breaking and entering, etc.
If you could use deadly force merely for the protection of property and nothing else, then spring-guns in uninhabited houses would be considered appropriate self defense; they're not. Even though self defense laws are often based upon whether a person is in your home, the law is still intended to protect people, not property, hence the term
self defense.