The last section of the story details Ennis's efforts to reclaim Jack's ashes from his parents. Or at least half of them, since the other half is interred with his wife. As Lureen informs Ennis, "He use to say he wanted to be cremated, ashes scattered on Brokeback Mountain" (128). Of course Ennis wants to honor that request and heads to Jack's parents for the other ashes.
But he just can't get it done: "In the end the stud duck refused to let Jack's ashes go. 'Tell you what, we got a family plot and he's goin in it'" (147). Ennis can't get him to budge. Oof. If that isn't a symbol for Jack and Ennis's doomed love, we don't know what is.
So what does it mean? Well, we suspect that it's a sign of the futility of their relationship: they have so little control over their life and their love that they can't even get buried the way they want to. It also highlights just how much other people (i.e., society) get to dictate their behavior and actions—even after they're gone. It's a hard-knock life for a gay cowboy, even when that life is over.