Billy hands the book of the Civil Law (Code) of the United States to Sam. Initially it is closed, the next shot shows that it is open, then the next shot shows that it is closed.
Cal takes Abby from Sam while holding his gun on him. When he gets back to the mob, Sam calls for Billy to "get his gun." At that point, Cal's gun is no longer in his hand.
Billy is walking behind the mob outside of the Marshall's office reading the Civil Law (Code) of the United States and doesn't see the mob until Sam calls to him to take Jeb's gun. This shows Billy to be an inept lawman.