allow (one) free rein
To give one complete freedom to do what one wants or chooses. Can you believe the boss allowed me free rein on this project? Finally, I can present a campaign with my own vision!
give/allow somebody/something free/full ˈrein
, give/allow free/full ˈrein to somebody/something
not restrict, limit or control something: In a novel the author need not keep to the facts, but a textbook is not the place to give free rein to your imagination. OPPOSITE: keep a tight rein on somebody/somethingA rein is a long leather band that is fastened around a horse’s neck and used by the rider to control the speed of the horse.