"an affair of honor"

This scene, where the Judge talks Couts out of arresting them for murder, seems unbelievable and makes Couts look a little stupid, until you bear in mind this incident summarised from Cout's diaries:

Couts seems to have also acquired the stereotyped traits of the "southern gentleman"—notably placing personal integrity above all else and a willingness to chastise those opponents threatening his honor. This became evident after an army officer, Major Justus McKinstry, verbally maligned Couts' new-found sweetheart, Ysidora Bandini. Incensed, Couts sent a friend, Lieutenant George Evans, with a note challenging McKinstry to a fight. Declining the summons, McKinstry chose instead to thrash it out with Evans in Old Town Plaza, much to the ire of Couts.