"Release."

Will Genia of Australia probes from a tackle/ruck with Victor Matfield and Chiliboy Ralepelle in front of him. Ralepelle grabs him and brings him to ground, holding him.

Genia is tackled.

Chiliboy stays on his feet. In terms of the law he is not a tackler however much tackling he may have done.

Law 15 DEFINITIONS
Opposition players who hold the ball carrier and do not go to ground are not tacklers.

Ralepelle is not a tackler.

In terms of the law he now falls into the category 'Other Players', and they are obliged to release the tackled player and go round and come in from behind the tackle and on their side.

Law 15.6 OTHER PLAYERS
(c) Players in opposition to the ball carrier who remain on their feet who bring the ball carrier to ground so that the player is tackled must release the ball and the ball carrier. Those players may then play the ball providing they are on their feet and do so from behind the ball and from directly behind the tackled player or a tackler closest to those players’ goal line.
Sanction: Penalty kick