My story takes place in in the 1800's. At that time the railroads and banks were using Pinkerton Detectives to guard their assets from the outlaws and bandits. My characters interact with outlaws and the people pursuing them during the course of the story. Are there rules or regulations against using real organizations to pursue fictional outlaws? Can I use the pinkertons or would I be better off creating my own fictional organization to go after them? Thanks for any insight!