Cattle King is a 1963 film directed by Tay Garnett. It stars Robert Taylor and Robert Loggia. It also appears to have been called Guns of Wyoming in some countries.
Both men argue their case before the cattlemens association to President Chester A. Arthur, who happens to be in Cheyenne for a visit. A hired gun of Mathews picks a fight with Brassfields top man, Johnny Quatro, in a saloon, then vows revenge after Brassfield intervenes.Brassfield proposes marriage to Sharleen Travers, who runs a neighboring ranch with her brother Harry. At first the spineless Harry sides with Mathews, but after a scolding from his sister, he apologizes to Brassfield. A while thereafter, the hired gun Bodine shoots and wounds the unarmed Harry, then kills Sharleen in cold blood. ........
Source: Wikipedia