That already is what the Law says
[TEXTAREA]Law 16 RUCK: DEFINITIONS
A ruck is a phase of play where one or more players from each team, who are on their feet, in physical contact, close around the ball on the ground. Open play has ended.
Players are rucking when they are in a ruck and using their feet to try to win or keep possession of the ball, without being guilty of foul play.[/TEXTAREA]
[TEXTAREA]
Law 16.3 RUCKING
(f) A player rucking for the ball must not intentionally ruck players on the ground. A player rucking for the ball must try to step over players on the ground and must not intentionally step on them. A player rucking must do so near the ball.
Sanction: Penalty kick[/TEXTAREA]