I watched Brokeback Mountain a couple of nights ago and then read the story again, and I noticed how carefully Annie Proulx lays out Ennis del Mar’s predicament. 
In the summer of 1963, when Ennis del Mar and Jack Twist met, Wyoming and Texas still had sodomy laws, and Ennis and Jack were subject to prosecution for what they did together in the pup tent. 
In 1967, when Ennis saw Jack for the first time after Brokeback, he tells him about his dad and his brother T. E. and about the tire iron and the bloody body in the ditch (p. 29). Whatever Jack thinks about this story, for Ennis the danger is real. He says, referring back to their kiss on the staircase, “We do that in the wrong place we’ll be dead” (p. 27). At the end of Brokeback Mountain, both the movie and the story, Ennis listens to Lureen tell him about Jack’s death, and he concludes, “They got him with the tire iron” (p. 45). 
Even before Ennis met Jack, he already knew what he was going to do with his life. “In 1963 when he met Jack Twist, Ennis was engaged to Alma Beers” (p. 5). That was settled.  “In December Ennis married Alma Beers and had her pregnant by mid-January” (p. 18). The reader isn’t told what Ennis actually thinks about what he’s doing. He does this, and then he does that, what’s expected of him. “The second girl was born” (p. 19), and he’s trapped. He doesn’t struggle. Lying in bed with Jack, Ennis says, “I like doin it with women, yeah, but Jesus H., nothing like this.” Then Ennis describes his problem. “Took me about a year a figure out it was that I shouldn’t a let you out a my sights. Too late then by a long, long while” (p. 26). Too late. But it’s too late in a different way than the one Ennis means. It was already too late by the time he finds Jack at the beginning back in 1963.
They can’t change what they are, and they can’t change how they feel, and they can’t get away from Wyoming—“All the travelin I ever done is goin around the coffeepot lookin for the handle,” Ennis says (p. 40)—and Ennis sums it up, “I’m stuck with what I got” (p. 29). It’s a mistake to read Brokeback Mountain as if it were about a man who made a mistake. Ennis did not make a mistake. When the guy came who presented him with an erect cock, Ennis knew what it was and what it was for, and what it meant. His tragedy is that he also knew he couldn’t do much about it. And he knew this from the beginning.
Ann Proulx, Brokeback Mountain, New York: Scribner, 2005. Originally published in The New Yorker, October 13, 1997. Page numbers in this posting are to this Scribner edition.

Brokeback Mountain, Director Ang Lee, Starring Heath Ledger, Jake Gyllenhaal, Anne Hathaway, Michelle Williams