What are the rules for defenders in the seven metre zone?

• The seven metre zone is the area between the seven metre line and the try line.
• When a defending player enters their own seven metre zone, the defending team must move forward at a reasonable pace until a touch is imminent or made. The penalty is awarded to the attacking team at the point of the infringement.
• When the player in possession enters the defending team's seven metre zone, the defenders are not obliged to move forward but cannot retire back towards their try line until a touch is imminent or made. The penalty is on the seven metre line in line with the infringement.
• When a rollball is in the defending team's seven metre zone, or a penalty tap is within ten metres of their try line, all defenders must have both feet on or behind their try line and no other body part on the ground forward of it. The penalty is on the seven metre line directly forward of the infringement.
• If the defending team is penalised three times on entering their seven metre zone during one possession, the last offending player is excluded until the end of that possession.

Source: FIT Playing Rules 5th Edition, rules 10.13, 10.14, 15.4 and 18.8.