I assume it's because they are afraid of introducing any number of citrus pests, blights, etc. into the lucrative citrus growing areas of these states.--I suppose you probably could add Florida to this list. Not quite as sure why Florida would ban the sale and shipping of citrus out of Florida into say--New Jersey. Not sure what the current laws are actually as these ARE subject to change depending on conditions. Good luck!

I know there's restrictions on citrus from FL. Maybe because of citrus canker? I don't think there's problems with citrus originating in CA. I think they can go anywhere. CA, AZ and HI have some of the most restrictive laws when it comes to shipping plants into the state.