I didn’t want to say anything because I didn’t want to be a grammar Nazi, but it’s happening more and more now so I think you should know. Because you want to do right, right? You want to use words correctly, even precisely, because that’s just how you roll.
So. Take a deep breath. It’s free rein. Not free reign.
The phrase comes from the equestrian arts. It refers to riding a horse with a loose rein, allowing the animal to move freely and even make certain decisions without interference. So when you give a person free rein, you are allowing that person to make certain decisions without interference. See?
Free reign makes no effing sense whatsoever.
And when you write it that way, you make even Sarah Palin cry.