This is not as unusual as you may think - especially with the little guys that like to think they are the boss.
It is impossible to say if this is dominance or past abuse but this suggestion - if consistent and really worked at - will work with both with the minimum stress.
Try feeding the other dogs normally but when the "non leash" dog is to be fed he must tolerate the leash for a short walk - say a quarter of the way down the garden - to his food bowl. When he is happy with this begin to increase the distance to the feed bowl.
Beware! If this is a dominance problem the dog will dig his heels in and still refuse to move. You must not give in, not even a little bit with a few treats!!!! If he goes hungry for a day it will not kill him.
Before trying this split his food into three meals a day for three days so that when you start the leash before food thing he is used to eating often and has plenty of time to decide he really is hungry. More to the point he has plenty of time to realise you are not going to give in!!
When he is happy with the garden you must make him walk a little further before each meal.