World Rugby have released the following information:
The definition of offside lines at the ruck have been changed in order to make them consistent with those at the tackle.
Recent events have brought the definitions of ruck and the creation of offside lines into focus. The references to hindmost foot are no longer reflective of the way the game is played or refereed. To that end all instances of “hindmost foot” should be replaced with “hindmost point of any player”, so as to remove the involvement of the foot as being the thing which dictates the offside line.
So for ruck law 15.4 – Offside at a ruck
Each team has an offside line that runs parallel to the goal line through the ruck participants’ hindmost foot. If that foot is on or behind the goal line, the offside line for that team is the goal line.
At a ruck or maul, the offside line runs through the hindmost foot of the player of the same team. The player in the yellow jersey on the right-hand side is offside.
15.4 Each team has an offside line that runs parallel to the goal line through the hindmost point of any ruck participant. If that point is on or behind the goal line, the offside line for that team is the goal line.
At a ruck, the offside line runs through the hindmost point of the hindmost player of either team. The player in the yellow jersey in the diagram below is offside.
There is also a simplification of the definition:
Hindmost foot: The foot nearest a team’s own goal line in a scrum, ruck or maul.
Hindmost: Nearest a team’s own goal line.