Kodi is, but it's a LOT of work, best started at a young age.
The MOST IMPORTANT thing, is that it's like potty training. You MUST set it up so that it's easy for the dog to do the right thing, and very hard for them to make a mistake. You must NEVER call your dog unless you are 95% sure that you can get him to respond immediately and with enthusiasm. Most people start with "Come, come C O M E ! ! ! " over and over, (while the young dog pays NO attention, or worse, purposely plays keep-away!) from a very young age. Dogs that have had this sort of start on the recall will be even harder to train.
And there are some breeds (notably sight hounds) as well as some individuals of other breeds that just can't be trusted to recall reliably in the open EVER. They are just wired to follow anything moving. They act completely instinctively, without even thinking.
I had three things in my favor with Kodi.
1. He is EXTREMELY people oriented, so his favorite thing is being with me anyway.
2. When he was learning to be off leash, he was accompanied by an older, well-trained dog that he adored. So we could call both dogs back together, and Kodi happily did what the older dog did. (and still got HUGE praise for it!!!)
3. Kodi and I have worked with EXCELLENT positive-based trainers from the time he was a small puppy. They (and reading TONS about positive training methods) helped me avoid many of the pitfalls that other people make. This hasn't been inexpensive, but has been extremely rewarding, both in terms of my dog's behavior and in terms of all the fun we have had working together.
Then it just takes a LONG time, and many, MANY positive repetitions to get (and KEEP) it reliable. Even now, when we are out in the woods, I ALWAYS have cookies in my pocket. Several times in the course of our walk, I will call him back to me, pat him and tell him he's wonderful, give him a cookie and release him. As a result, when I see someone coming toward us on the tracks with another dog, even if he heads toward the dog, I can call him back, and he will turn right around and come back to me. I don't have to worry about him getting in any trouble with a reactive dog.