God owns all the land. If Bundy’s family has made use of it since the 1800’s then in my eyes it’s theirs until THEY sell it.
Suppose you owned a vacation property of say 10 acres and that you had a nice cabin on it. You visit it once a year and you have a fence on it to “mark” your land. Then without your permission, or knowledge, one of your neighbors digs up your fence posts and moves them into your land so that they gain some of your property. If you don't assert your property rights to that now disputed land, you could lose that land to “adverse possession”