All domestic ducks, other than Muscovies, are descended from Mallards. The bird from the original post has a lot of tan coloring and a lot of white on the wings, and cannot be a wild Mallard. It just looks like a mixed breed to me. No wildlife ranger is going to mistake that for a wild Mallard...
There are wild Mallards, which are illegal to keep, and domestic Mallards, which are legal to keep. The bird in question is definitely not a wild Mallard and I don't think it is a domestic one, either. Looks like maybe a mixed breed to me.