My rabbit lived for 10 years and spent most of his life in the garden, usually coming out first thing in the morning and not going in until we made him when it was dark! As long as it is secure and there are not cats roaming your area, he will have a much better life in the garden than in a hutch, so I think it is worth the risk. Also his diet will be much better as he will be eating grass in the garden which is what rabbits were designed to eat, not the terrible rabbit mixes available from pet shops (grass pellets and hay are much healthier as long as they do not contain alfalfa). I would recommend however that you don't leave him out if there is no one in for a very long length of time or after dark. You may also want to consider getting him vaccinated for myxomatosis if you haven't done this already; this is a fatal disease spread in the environment by wild rabbits. Good luck with your free range bunny!

Make sure no cats or other predators can get into your garden. My cousin had a baby rabbit once, she used to let him out in the yard to eat grass. A neighbourhood cat got in one day and let's just say she doesn't have a pet rabbit any more.