I found the Sanford Police Department Neighborhood Watch Program guidelines:
http://www.sanfordfl.gov/investigation/docs/NWProgramHandbook.pdf
Thank you! I was looking for that through National Neighborhood Watch, and didn't think about looking through the police department.
Quotes from the pdf:
What you will not do is get physically involved with any activity you report or apprehension of any suspicious persons. This is the job of the law enforcement agency.
*snip*
Remember always that your responsibility is to report crime. Do not take any risks to prevent a crime or try to make an arrest. The responsibility for apprehending criminals belongs to the police department.
http://www.sanfordfl.gov/investigation/docs/NWProgramHandbook.pdf
Fascinating, but nowhere in that document does it say that a Neighborhood Watch person can or cannot carry a weapon, and I guess Florida law trumps that anyway. However, it states several times that if you see a person who might be carrying a weapon that is a valid reason to call 911, which struck me as highly ironic since almost anyone might have a weapon, and George certainly did.
It also never states whether a Neighborhood Watch person is supposed to go out on "patrol," but we know that's what George was doing.
The main thing I get from that document is that NW is for "watchers" who should let police handle things. George didn't quite understand that part.