É da altura dos ombros para baixo que um jogador pode ser agarrado, ou seja, não pode ser atingido no pescoço e nem na cabeça.
É verdade. Mas mesmo assim as regras do rugby exigem juito mais cuidado no tackle, veja:
"Rugby union rules do not allow tackles above the plane of the shoulders. Only the player who has possession of the ball can be tackled. The attacker must also attempt to wrap his or her arms around the player being tackled: merely pushing the player being tackled to ground with a shoulder is illegal. If a maul or ruck is formed, a player may not "ram" into the formation without first binding to the players.
In American football, tacklers are not required to wrap their arms around the ball carrier before bringing him to the ground; in fact, the ball carrier is often "tackled" by the defender taking a running start and hitting the ball carrier to knock them to the ground. Tackles can also be made by grabbing the ball carrier's jersey and pulling him to the ground (though pulling down a ball carrier by the pads behind his neck is known as a "horse collar", a move now illegal at all levels of the American game). If a ball carrier is stopped for more than a few seconds, the referee can blow the whistle, declare the player's forward progress stopped, and end the play even though the ball carrier is not actually tackled to the ground.
In American football, players are allowed to 'block' players without the ball, this is not permitted in rugby union and would be considered 'obstruction', resulting in a penalty."
http://en.wikipedia.org/wiki/Comparison_of_American_football_and_rugby_union
