World Rugby has issued guidelines for applications of laws governing the breakdown, which aims to prevent defenders from poaching the ball.
The 'jackal' style stripping of the ball is seen as the cause of a large number of injuries, with players' backs and necks vulnerable to strong impacts while they are crouched at the ruck.
The new rules limit the players who can compete for the ball at the ruck.
It will come into force from 1 July after recommendations from a specialist breakdown working group made up of international coaches, players, medical, laws and research experts.
Covering Laws 14 to 15, World Rugby added that it "reinforces the application of current law for what is a complex and dynamic facet of the game."
Limiting the players who can contest at the ruck may lead to increased numbers in the defensive line, which is something World Rugby are also attempting to address, with trials of the so-called 50:22 rule, which encourages more kicking into opposition red zone and therefore may lead defending teams to keep more players in backfield.
Tackler (Law 14): 14.5 – must a) Immediately release the ball and the ball-carrier after both players go to ground and b) Immediately move away from the tackled player and from the ball or get up.
Ball Carrier (Law 14): 14.2 – Being brought to ground means that the ball-carrier is lying, sitting or has at least one knee on the ground or on another player who is on the ground. 14.5 – Tacklers must: d) Allow the tackled player to release or play the ball.
First arriving player (Law 15): 15.11 – Once a ruck has formed, no player may handle the ball unless they were able to get their hands on the ball before the ruck formed and stay on their feet. 15.12 – Players must endeavour to remain on their feet throughout the ruck.
Other arriving players (Law 15): 5 – An arriving player must be on their feet and join from behind their offside line. 6 – A player may join alongside but not in front of the hindmost player. 10 – Possession may be won either by rucking or by pushing the opposing team off the ball.