The justification is so wealthy landowners can have their own little slice of beach away from the plebs and not have to deal with everything that comes with being a public beach. The trouble is, they want their private beaches but still expect the government to pay for replenishment. The way it works in NJ is that if federal money is used for beach replenishment or maintenance, that beach must have a management plan that incorporates things like public access and endangered species protections. These people who try to claim their beaches are "private" are actually wrong and get very pissy when you call them on it. Accept public money, allow public uses.