Owner Guarding.....

Dogs may be selectively aggressive when approached most notably approach by other dogs, through people can also be targets, if they are in proximity of their owners or when on leash.  Some owners find the "jealous" behavior flattering or amusing, while others are distressed.  Owners often attribute the behavior to "protectiveness."  The topography of the behavior is identical to other kinds of resource guarding, and it responds to the same kinds of treatment exercises, so it would seem logical to consider the owner to coveted resource in these cases.