Your question is exactly the sort of thing that will come forward in the next weeks and I am more than happy to answer (correctly I trust).
OK. In your scenario below;
- The corner post is a dead element (so no decision need be made because the ball hit the post)
- It is important to know what happened to the ball AFTER hitting the post (the flag itself is irrelevant)
After the ball hits the post I see four different possibilities (and I have added their outcomes);
Bounces back into the field of play – play on
Bounces into touch (as in your scenario) – line-out for the attacking side minimum of 5 meters from the goal-line (lets ignore quick throw-ins etc for the moment)
Bounces into in-goal – Defence could decide to ground the ball (resulting in a 22 meter drop-out) or play on – they can run the ball out and/or kick directly into touch - they will receive a gain in ground (presuming they manage to get the ball out of their in-goal)
Bounces into touch in-goal – this will result in a choice for the defence – 22 meter drop-out or a scrum at the place the ball was kicked
So well thought out by you,
Cheers
Sean