A scissors or bicycle kick is permissable provided that, in the opinion of the referee, it is not dangerous to an opponent
(pg115) http://www.fifa.com/mm/document/affe...e_2011_12e.pdf
as I said down to individual interpretation one ref could say it was dangerous and another say not, even if a player isn't in contact with the kicker. If I was a ref and there was a player within 1 metre of the raised feet I would consider that dangerous in case a player attempted to get the ball.
You seemed to be suggesting it came under the law about whether you have two feet on the ground or not, it doesn't. It is it's own line in the laws of the game apart from anything to do with how many feet are on the ground.