Does a swimming pool have to have a fence?

All in ground pools and above ground pool with a wall height less than 4 ft. requires fencing, with the exception that an in ground swimming pool that is located on five acres or greater is permitted to be secured with an automatic pool cover that meets the American Society for Testing and Material Standards (ASTMF1346-91) in lieu of a fencing.  Above ground pools with a wall height greater than 4 ft. does not require a fence but must be secured when not in use with a removable or lift up locking ladder.