OK. Must not have read it in the IRB rules, but it is mentioned in the 2014 ARU Game Management document
http://www.rugby.com.au/Portals/22/2014 Laws/2014 Game Management Guidelines.pdf
However, the off-side offence has to occur before the ball goes into touch. Without seeing the Stormers incident, I don't know if it is applicable.
OFFSIDE IN GENERAL PLAY
Rationale for emphasis
• When the ball is kicked in general play, any player of the kicking team in front of the kicker is offside.
• Offside players who are advancing are cutting down options for counter attack and forcing the receiving team to kick as their first option. Referees must penalise offside players and should no longer rely on continually verbally managing these players because by advancing they have already had an impact on play.
• With a long kick downfield, referees
may be able to manage an offside player. The referee should call only
once for the player to stop. If the player does not stop immediately (not just slow down), they are liable to penalty.
• With a short or high kick, there will be little or no opportunity for the referee to manage and players must immediately act as per Law or they are liable to penalty.
• Offside players must be dealt with
even when the ball looks like it will go into touch because a quick throw may be an option. Once the ball is in touch, offside no longer applies and offside players may move forward toward a lineout or where a quick throw is being attempted