"We need to be clear about this... we cannot allow player welfare to be put at risk by shoulder charges," Greenberg said in a statement.
"A player carrying the ball cannot protect himself properly against the force of a shoulder charge.
"We have seen this type of tackle have tragic consequences recently and the NRL has an obligation to put player safety first."
Greenberg said players found guilty of shoulder charges risked lengthy suspensions.
A grade one shoulder charge offence carries a base penalty of 200 points and more serious breaches can result in suspensions of up to eight matches or more.
"In other words, anyone found guilty of using a shoulder charge with force will be suspended for at least one match," he said.
"So there will be a real incentive for players and coaches to ensure that shoulder charges are taken out of the game."
-AAP