Here in Australia, it is illegal to practice falconry. Falconry is a sport in which game is caught by a trained raptor in cooperation with a falconer. It is, however, not illegal to train raptors to free fly for the purposes of rehabilitation in Western Australia. This is not falconry, nor are the rehabilitators falconers.
Free flight is extremely beneficial after wing injuries or long term hospital care. Bird catching falcons need huge spaces to exercise well, because they fly fast, and cover large distances very quickly. Training young bird catching raptors hunting strategies to catch prey is also impossible in a flight pen. Younger raptors should be hacked out, or soft released as they fledge. If they can't be released until after fledging, they will not stay to be fed at a hack site. (Releasing a bird catching raptor that has never hunted before is a death sentence.)
The drawbacks to free flying raptors are that the process is very time consuming, and that the person doing it must be well trained. If you are considering this option, and you can't train your dog to do tricks, forget it. Raptors are much harder to train than dogs. They are not inclined to please, and because their relationship with you is built on trust, (not love) you can not use any kind of punishment (which the birds do not understand, anyway).
Training centers on building a routine of behaviours with food rewards. It mimics the hunting process. As soon as the bird is let out to fly, it is free to go. It returns to it's handler by it's own choice. This training technique gets the raptor to focus on the trainer as a food source, and means the raptor is fed every day while it learns to hunt, or regains it's strength and stamina. So this is very similar to hacking or soft releasing fledgling raptors, but can be done with older birds that wouldn't otherwise stay in the area.
Critics have said that trained birds become tame, and that all their fear of humans is lost. This is certainly not the case. For more details, see "To Tame or Not To Tame". Human imprinting is a separate problem, which occurs when raptors are hand raised improperly from a very young age. In some species, even this can be reversed. Manning, where a full grown raptor is habituated to being around it's trainer, is learned. It is a trust relationship where the raptor learns that a particular human is not going to harm it, and that the human will also show it where there is food. Given their incredible eyesight, it is not surprising that they will recognise their trainers, and many will continue to fear strangers unless they are introduced slowly to other people as being 'safe'. Once a manned raptor is fat, and out of the habit of coming to it's trainer, as it should be after release, it has no reason to come towards people. In a very short time the bird forgets about people and gets on with being a wild bird.
Some people also criticise free flight training techniques, claiming that raptors are starved, and that they return because they are extremely hungry. While some people may treat their raptors this way, such birds are physically unable to gain muscle, and will never get fit enough for release. The birds that are correctly trained have their weight monitored. A fat bird will go without food for a day quite contentedly. This is a natural strategy to conserve energy in the wild. Birds only hunt when they are hungry, or when it is easy to catch the prey. They react the same way to their trainer and the food rewards.
Weight monitoring is used to find the bird's 'trim' weight, and to know when it will be a little hungry. When it is taken out to fly, it is interested in hunting, so the trainer brings out a lure to simulate prey. A falcon can do several passes at the lure without quite catching it, and will get good exercise. Once the bird is allowed to grab it, it is rewarded with a small snack if it will do another 'hunt', or the whole meal if it is tired out for the day. This is continued as a routine until the bird is flying well. When the raptor is fit for release, it is fattened up and released once again. Being full, the bird is most likely to cruise off or go sit in a tree. By gradually letting the bird get fatter, the trainer is not the center of the raptor's attention, and it will wander around the area and practice hunting. For an experienced bird, this happens very quickly, and they will abandon the rehabilitator and revert to their wild ways. Raptors that have not hunted before take more time, as they must practice and perfect their hunting techniques before they can be independent.
Anyone considering training and free flying a raptor for rehabilitation has a responsibility to get advice from someone with several years of experience. While the basic concept is very simple, there are a lot of little details to the techniques that are critical to success.