Yes you can. Its called the Americans with Disabilites Act and if it is an "unfair" advantage, why isn't he out there winning tournaments? An advantage gives someone a means to have a leg up on everyone else. It isn't an advantage if you are using it just to have a fair shot. I fail to see how using a golf cart helps your golf game anyway. It doesn't help his golf game, it helps him survive and any reasonable person would know that it isn't an advantage.