Law 15. side entry to the ruck.

Jacques Botes of the Sharks, makes a tackle and Louis Ludecke, the Sharks wing goes to contest. The Chiefs hooker, Mahonri Schwalger, sees this and runs in from the side to remove the threat. The referee then gives a penalty to the Sharks for side entry into the tackle.

Law 15.6 (d) At a tackle or near to a tackle, other players who play the ball must do so from behind the ball and from directly behind the tackled player or the tackler closest to those players’ goal line.
Sanction: Penalty kick

The same “gates” through which a player must enter the tackle to play the ball, applies to both attacking and defending teams, and far too often, the attacking side, gets away with this type of entry.

A good penallty by the referee, and a text book case of attackers side entry

The Sharks are on the attack and Craig Burden makes a line break after a ruck. Burden is tackled. The tackler, Hika Elliot (16) of the Chiefs, does enough to convince the referee that he has released and got to his feet to contest for the ball.

Law 15.4 THE TACKLER
(a) When a player tackles an opponent and they both go to ground, the tackler must immediately release the tackled player.
Sanction: Penalty kick
(c) The tackler must get up before playing the ball and then may play the ball from any direction.
Sanction: Penalty kick

But of interest in this clip is the action of Chiefs Augustine Pulu (20). He does not enter through the “gates” and further more, he then goes beoynd the ball and “takes up space” to obstruct the Sharks players and prevent them from cleaning out Elliot and remove him as a threat.

Law 15.6 (d) At a tackle or near to a tackle, other players who play the ball must do so from behind the ball and from directly behind the tackled player or the tackler closest to those players’ goal line.
Sanction: Penalty kick

Law 15.7 (d) Players on their feet must not charge or obstruct an opponent who is not near the ball.
Sanction: Penalty kick

Pulu’s action buys enough time for Elliot to steal the ball and he was lucky not to get penalised for side entry at the tackle and for obstructing the Sharks’ arriving players.