WordNet (r) 3.0 (2006):

free hand
    n 1: freedom to do as you see fit; "many have doubts about
         giving him a free hand to attack" [syn: free hand, blank
         check]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "free hand":
   ample scope, bigheartedness, blank check, bounteousness,
   bountifulness, bounty, carte blanche, clearance,
   easy purse strings, elbowroom, field, free course, free play,
   free scope, freedom, freehandedness, freeheartedness, freeness,
   full authority, full power, full scope, full swing, generosity,
   generousness, givingness, graciousness, great heart,
   greatheartedness, hospitality, largeheartedness, largeness,
   largess, latitude, leeway, liberality, liberalness, long rope,
   magnanimity, maneuvering space, margin, munificence,
   no holds barred, open hand, open heart, open mandate, open space,
   openhandedness, openheartedness, play, range, room, rope, scope,
   sea room, space, swing, tolerance, unselfishness, way, welcome,
   wide berth