Ah, the old "someone LG must obey all laws of the land argument". No mention of whether the people running things are corrupt or simply incompetent, whether the laws are just and good, nothing. Is a LG person going to suddenly start supporting slavery because they cross the border?
That, and it doesn't really matter what alignment Batman is. First there have been dozens of implementations of Batman over the years, it's not like they've been terribly consistent. Second, a person can be LG because of their own strict rules such as the no killing rule. Last but not least it doesn't really matter what anyone else thinks other than the person running Batman. It's just a descriptor, not a straightjacket. Find it useful? Cool. Don't? Ignore it.