Might be legal, but definately stupid. If your not very careful when you build it the ground can erode or become soft and your foundation may sink, shift, or crack. Something that costs massive amounts of money to fix. Also, think about the effort to clean it. You would have to take the aligators out and scrub the whole thing down. The black knight could just sneak in when it was drained and the gators were locked up. They are not dog or child friendly and most neighborhood association won’t allow them. You’ll also have a huge water bill.
is it legal to build a moat? - yahoo answers