Infraction/Error:
Ashe played Pithing Needle without paying the proper cost for the spell which is 2 due to Thalia, Guardian of Thraben.

Penalty:
Ashe - GPE-GRV - W - Paid 1 instead of 2 for Pithing Needle due to Thalia
Norman - GPE-FtMGS - W - Fail to notice the error from Ashe and allowed Pithing Needle going to graveyard.

Remedy/Fix:
We will rewind the play till before casting the Pithing Needle since the error is caught in short amount of time.

Some references below from last few Knowledge Pool:
A-rushin into trouble
To Bee, or Not to Bee

GPE-GRV for Ashe, GPE-FtMGS for Norman.

The spell was improperly cast, so we rewind the game to before the spell was cast. No significant actions have been taken since the spell was placed on the stack, so a rewind is reasonable here. We warn both players to be more cautious in the future.

It seems like the question of whether to back up or not hinges on what, specifically, the error comitted is. Per the IPG 1.4: “A good backup will result in a situation in which the line of play remains the same (excepting the error, which has been fixed),” as others have noted.

Case 1: The error is: {cast pithing needle for an incorrect mana cost}.

In this case, the phrase “the error” refers to the entire casting of pithing needle. The rewind would be warranted in this case, since fixing the error would result in Ashe not casting pithing needle for an incorrect cost, even though the rewind potentially opens up alternative plays. Since chalice is an ‘on-board’ counter, no additional information is revealed, so the fact that Ashe forgot about it should not matter to whether we rewind or not.

Cons: Ashe now may opt to not cast pithing needle, potentially opening up new lines of play. It is not necessarily clear that the ‘broken gamestate’ (with mana tapped and pithing needle in the graveyard) is substantially worse than the backed-up gamestate.

Case 2: the error is: cast pithing needle {for an incorrect mana cost}.

In this case, “the error” is specifically the failure to pay Thalia's ‘tax’ on pithing needle. In this case, a rewind will be less desirable, because we want to preserve the casting of pithing needle, but we want to have to correct cost paid. A rewind would open up new lines of play since Ashe could opt to do something else with the mana instead of cast pithing needle.

Cons: Philosophically, since we are seeking to preserve the casting of pithing needle, we would open ourselves up to backups that result in us being in the middle of casting a spell, which is not a place where you can terminate a backup. this seems inconsistent with the example given in the Annotated IPG of a player casting terror on a White Knight. applying the reasoning of case 2, we would only want to back up to the choosing of targets for terror, rather than prior to the casting of terror, in order to avoid opening up ‘new lines of play.’ To the best of my knowledge, this kind of backup is philosophcally incompatible with the IPG, since then we would only authorize a backup if there were a legal target for terror currently in play, and otherwise we would leave terror in the graveyard every time.

My own thoughts are: The presence of Chalice of the Void in play is a red herring. If Ashe had illegally cast pithing needle into a board of just Thalia, there would be no case to be made for leaving the board state as it sat, and we would authorize a backup, even though Ashe might opt to play something else instead. The fact that there is another effect in play that Ashe has forgotten about should not affect our decision of whether to back up or not. The decision tree in this example is only whether or not to cast needle, and that is not too much of a decision tree to back up through.

Tl,dr: It seems more consistent with the philosophy and practice of the IPG to back up than not to. The presence of Chalice in play is a red herring, since its presence makes it seem more likely that Ashe will not cast pithing needle after a backup. However, Ashe always has that option, even in cases where a backup is clearly warranted, so that consideration should not outweigh the damage to the gamestate caused by leaving it as it sits presently (mana tapped, needle in graveyard).

Ruling: Ashe: GPE-GRV warning, Norman: GPE-FtMGS warning, remedy: rewind to the point just before the casting of Pithing Needle

Edited Andrew Keeler (April 11, 2015 05:20:27 PM)

So looking back on this and doing some reading, as well as talking to others about it, the only time a double GRV applies is if one player (P) controls an object that is telling the other player (OP) to take an action. If OP does that action wrong and P allows it to happen, or both players do that action wrong, then it's a double GRV.

If P has no part of the actions taken wrong other than simply not noticing it, then it's GRV / FTMGS.

Also something interesting that I hadn't really thought about but kind of assumed, if a player casts a spell wrong (illegal choice or target or they paid mana wrong, or anything else in casting a spell) we back up to the point they had priority just before they cast it.

However if a player resolves a spell wrong, we back up to the point where it was put on the stack instead, assuming we can back up in the first place.

It's a clear GPE-GRV, GPE-FtMGS situation when a spell is cast for the wrong cost. It can't be rulled GRV, GRV because thalias has a “passive” abilitie, this is for cases like not making sure your oponnent puts the land from a Path to Exile in play tapped.
There's no partial fix for this situation and we can't rewind because it's almost certain that the information gained will change the decision tree, it's very unlikely that someone will play the needle knowing it will be countered.

Hello Judges! Thank you very much for this week's discussion; it was just what we wanted. Also, a shout-out to Matteo Callegari for inspiring this post with his seminar on backups.

Pretty much everyone agreed that our friend Ashe had committed a GPE - GRV for casting the her Pithing Needle and paying the wrong amount, thanks to a Thalia, Guardian of Thraben on Norman's side of the board. But what to do with Norman?

Some suggested he should be getting a GPE - GRV too, as he controlled the effect that caused Ashe to commit her infraction. However, as several others noted, Thalia has a static ability that isn't actively forcing Ashe to do something; as opposed to Swords to Plowshares or similar. It's a FTMGS for Norman with a simple warning attached.

Now, to back up, or not back up? That is the question…

Most arguments in favor of backing up noted that very little time had passed and that nothing major had really happened. Some even cited CR 717.1. Had Ashe's mistake been caught before anything else happened (Chalice of the Void's trigger resolving), CR 717.1 would apply automatically and we'd be forced to back up, as we'd be caught in the middle of an illegal action. However, we've moved past that point and are currently sitting at a legal board state; the Needle is sitting in the graveyard and nothing else is going on, so CR 717.1 doesn't apply.

The KP team feels that although few game actions have happened and the error was discovered very recently, it is not a good idea to back up. As per IPG 1.4 - Backing Up (emphasis mine):

Due to the amount of information that may become available to the players and might affect their play, backups are regarded as a solution of last resort, only applied in situations where leaving the game in the current state is a substantially worse solution. A good backup will result in a situation where the line of play remains the same (excepting the error, which has been fixed). This means limiting backups to situations with minimal decision trees.

There is very little chance that the line of play here will remain the same, as Ashe will likely not play the Needle again. A backup would have to go all the way back to before she cast the Needle, and once we get to that point, there is basically no reason for her to cast it again. Leaving the board as is isn't substantially worse than having Norman gain information on Ashe's hand and have Ashe make a completely different play, so our ruling is to not back up.

Thanks again for your participation. We hope you enjoyed the scenario. See you in the next round!

GRV for Ashe and FtMGS for Norman. Warnings for both. As with others, I'd rewind to the point just before Ashe cast the Needle.

In regards to the advantage Norman would gain from knowing the Needle is in Ashe's hand, this is no more advantageous than if Ashe had simply revealed the Needle in her hand which is not against the rules. If we back the game up to this point, we have arrived at a game state that could have normally been reached by completely legal means while leaving the Needle in the graveyard does not.