Who call the seconds, regulate the mode of fighting and enforce the rules the fights have agreed on?

A duel has been described as a kind of fight between 2 persons, pre-arranged and fought with selected weapons usually in the presence of witnesses. The witnesses call the seconds, regulate the mode of fighting and enforce the rules the fighters have agreed on.
   Duels were fought over differences of opinion, real or imagined wrongs or insults, personal quarrels on honor.
   The custom of dueling, began in the Middle Ages, was brought to America by English settlers.
   It was a social practice that was common in various sections of the United States prior to 1870, and then are records of duel in the English colonies dial probably occurred at Plymouth. Massachusetts as early as 1621, though available records show fewer than 20 between 1624 and 1763. About 1780, after the Revolutionary War, dueling lost favor in the northern states but spread in the South until the Civil War. A growing class of plantation owners and an individualism that encouraged the development of a code of honor, both contributed to an interest in dueling in the South. It was not until after the Civil War, about 1870, that dueling declined in the area.