The high tackle warning will also be trialled in Top 14 and the Pro D2.
The approach is driven by an unprecedented study of more than 1,500 elite matches which confirmed that 76 per cent of concussions occur in the tackle, 72 per cent of concussions in the tackle sustained by the tackler and the risk of injury is 4.3 times greater when upright.
Other rule amendments that World Rugby will trial include a 50:22 kick, similar to rugby league's 40-20 rule. The reasoning behind it being it would create space as players would need to drop out of the defensive line. It will be trialled in the Americas Rugby Championship, South Africa's Varsity Cup and Italy's Top 12 competition.
Reducing tackling to the waist will also be trialled in youth and female competitions.
Other law amendments include the ability to review a yellow card when a player is in the sin-bin for dangerous foul play, the introduction of an infringement (penalty and free-kick) limit for teams, and a goal-line drop-out instead of 5m scrum when an attacking player is held up in the in-goal area. World Rugby has stated which competitions these new laws would be trialled.
What is a high tackle technique warning?
A high-risk contact tackle technique warning can be issued to any player where the tackle is upright (i.e. not bent at the waist when tackling), and there is clear and obvious head contact for either player.
The sanctions will be policed by both the match officials and the citing commissioner. When two high-risk tackle technique warnings have been issued, a player will automatically receive a one-match suspension.