There is nothing in the Rules of Golf preventing the person from fixing the sole of the shoe or the shoe itself to prevent swaying. However, if he is a walker, rest assured that he will be a very uncomfortable puppy after 18 strenuous holes.

hi. take the shoe . right shoe . the shoemaker puts a small piece of plastic . 3 inches long . 3/4 inch hi9gh. at the back of the shoe to the sarch. this causes legs to stay stable, forces right knee to stay stable , and foot connected to rthe ground . it does work. please stay away from shoemakers in a mall just go to a small shop. a very high number of medical staff have the same thing done to thier shoes. when you tell the shoemaker what it is for. he will understand. it is a very simple illegal adjustment . the shoemaker will have you wait . cost under ten bucks. go for a walk before playing with the brace. after two months you could have it removed . there were shoes built this way early 90s . they worked so usga banned them . ken venturi, ben hogan, sam snead and byron nelson to name a few used this method . good luck . sorry spelling eyes screrwed up from cancer hack saw surgery .