The Rugby Football Union has ruled two of the most controversial new experimental laws will not be trialled by youth rugby in England on safety grounds.
The RFU's management board approved a proposal that collapsing the maul will not be permitted in England at Under-19 level and below.
The experimental rule stipulating a player's shoulders must not be lower than the hips at a maul will also not be applied.
The RFU's move is a significant challenge to the International Rugby Board's attempts to push through a raft of new experimental laws into the game.
The RFU will not reconsider their stance until both new laws are "demonstrated to be safe in the adult game" and three other chief criteria are met.
Junior rugby has been up in arms since the IRB announced these two experimental laws would form part of a limited package being applied to the world game for a year from August 1.
RFU chief executive Francis Baron said: "We have received a large number of letters from the youth game expressing serious concerns over the introduction of some of the ELVs (Experimental Law Variations) in the youth game.
"It is established practice that unions can apply variations to the laws at youth level and many unions exercise their rights in this respect.
"The RFU intends to exercise its rights in respect of the ELVs of concern to us and the game in England following discussion with the IRB and other affected unions."
Those discussions will cover the issue of any cross-border competition where other unions have decided to trial the new laws at age-grade level.
But the RFU are not in a mood to compromise, adding: "The interests of young players and the safety concerns expressed by the game will take precedence."
The RFU will hold their position until the results of trials currently taking place in South Africa have been "properly analysed by the IRB, with specific reference to the safety of pulling down the maul at all rugby played at Under-19 and below".
Even then, the RFU insist the introduction of the laws will not be immediate.
They state agreement must be reached on the safest method to pull down the maul and appropriate coaching techniques developed.
And they want to ensure sufficient time to ensure those findings are communicated to all those involved in rugby at Under-19 level and below.