THE LAWS OF THE GAME OF RUGBY 6.A.7 REFEREE CONSULTING WITH OTHERS (a) The referee may consult with touch judges in regard to matters relating to their duties, the Law relating to foul play, or timekeeping. (b) A match organiser may appoint an official who uses technological devices. If the referee is unsure when making a decision in in-goal involving a try being scored or a touch down, that official may be consulted. (c) The official may be consulted if the referee is unsure when making a decision in in-goal with regard to the scoring of a try or a touchdown when foul play in in-goal may have been involved. (d) The official may be consulted in relation to the success or otherwise of kicks at goal. (e) The official may be consulted if the referee or touch judge is unsure if a player was or was not in touch when attempting to ground the ball to score a try. (f) The official may be consulted if the referee or touch judges are unsure when making a decision relating to touch-in-goal and the ball being made dead if a score may have occurred. (g) A match organiser may appoint a timekeeper who will signify the end of each half. (h) The referee must not consult with any other persons.
As I understand it, the referee ruled (erroneously) that the Hurricanes had knocked the ball on prior to entering the in-goal. This is an infringement which falls outside the scope of TMO review. The knock-on call was clearly wrong but, as the first infringement, this infringement was called first and prevented the following matters from being referred to the TMO.
However, if the referee had not ruled that there was a knock-on, the issues that followed clearly could have been referred to the TMO: - Waldron arguably scoring the try (6.A.7(b)); - Smith being tackled without the ball in-goal (6.A.7(c): tackling without the ball is foul-play under 10.4(f)).
Some might argue for greater scope to refer matters to the TMO, especially as (say) the NRL gives these officials greater review powers. But limits need to be drawn somewhere. On the one hand, we want the laws to be complied with and enforced accurately. On the other hand, allowing review of every decision creates logistical nightmares and disempowers the referees.
There's some analogy to be made to the law of judicial review where Parliament enacted privative clauses - ousting the jurisdiction of the High Court to review errors made by officials - to provide legal certainty (although our courts have largely read these down to make them nugatory). Similarly, the courts themselves have recognised that, in some cases, some issues are simply non-justiciable (ie not properly subject to judicial determination) because, amongst other reasons, review by the courts would usurp the constitutional allocation of functions and the courts processes are not suitable to reviewing such challenges.