Yes AL... you can lose it,.. for whatever reason.. You could even lose AL to another player, if they kill you and hold your land for long enough time. There has never been anything that guaranteed you would keep anything you buy on the marketplace.
As in.. The risk of loss is there for everyone.. Not just the Gentry. A King, Duke, Count or Mayor can still loss their lands. They can loss their tittles. There is nothing in place that will guarantee that this does not happen.
Those persons do not OWN the land that is in their domains... In truth they do not even own their domains. They would only own land as much as any other AL owner does. Because those persons would have the same access as everyone else to AL.