Free Rein Meaning

(idiomatic) the absence of constraints; freedom to make decisions

Example: loose rein, as of a horse
1884, Elizabeth Platt Karr, "The American Horsewoman", page 256,
  she should simply hold the reins so lightly that his mouth can just be felt, which is called "giving a free rein."
1910, Virgil (translated into English by Theodore C. Williams), page 8,
  So ceased the sea's uproar, when its grave Sire
Looked o'er th' expanse, and, riding on in light,
Flung free rein to his winged obedient car.
1913, Charles George Herbermann, Edward Aloysius Pace, Condé Bénoist Pallen, Thomas Joseph Shahan, John Joseph Wynne, "The Catholic Encyclopedia: An International Work of Reference on the Constitution, Doctrine, Discipline, and History of the Catholic Church", page 647,
  securing for himself an undivided authority and a free rein for his profligacy.
1861 New York Times, Aug 6, SLAVERY AND THE WAR.,SPEECH OF WENDELL PHILLIPS, ESQ., AT THE CELEBRATION OF WEST INDIES EMANCIPATION
  Help the Government to dare to give free rein to the ardor of the people.
1790 Thomas Pennant in Of London page 47
  Chaucer gave a free rein to his poetical mirth