From Richard Every at USAR (9/8/17, 1135; this is an excerpt since we’ve all seen the video and know the new law):
If a player has to step with one leg over the ball, they would be a prone target to be cleared out.
AT THIS TIME, in the USA, WE WILL DO THE FOLLOWING, until further clarification:
If, at a tackle, a player on their feet positions themselves over the ball, a ruck is formed. That means, your body has to be over the ball. It should be in a controlled manner, and both legs can still be on your side of the ball and they may grasp their player that is on the ground. Try not to over-complicate it.
If that player then decides to play the ball, they have to step back so they are no longer over the ball, then play the ball coming through the gate.
If, after they have formed the ruck, they pick up the ball in that ruck-forming position, it is a PK against them for hands in.