Originally posted by Violet Edgar:
If the player actually had had a swamp in the library… even then I'd have a problem with it, because technically they'd be gaining information that might influence their decision (“oh, Nono has a Wasteland in hand? guess I'll grab a basic swamp rather than a Scrubland”).
I feel obligated to point out that we're playing Standard in this example, so the only possible target for the Mire that can cast Thoughtseize is a Basic Land— Swamp.
To me, this feels just fine for out-of-order sequencing. Astro proposes a shortcut of “I'm going to use this land to find a land that can cast this Thoughtseize, but in the interest of saving time, let's resolve Thoughtseize first, and I'll search and shuffle during your turn.” Correct me if I'm wrong on this one, but in general, I'm okay with players doing this.
The MTR guidelines for Out of Order Sequencing apply here instead of Tournament Shortcuts. This is because a shortcut is “an action taken by players to skip parts of the technical play sequence without explicitly announcing them”. In this case, no action is skipped in the resolution of the abilities. Technically, they are also shortcutting to the beginning of Nono's turn, but that's not quite relevant here.
So, in the OoS rules, we see that “all actions taken must be legal if they were executed in the correct order”. So, let's look at the actions in order: Play a land. Check. Activate land's ability. Check. Resolve land's ability, in this case being unable to find a Swamp.
This is where my answer finds a wrinkle. The paragraph “an out-of-order sequence must not result in a player prematurely gaining information which could reasonably affect decisions made later in that sequence” seems to have multiple applications. The first is that in resolving Mire's ability, Astro would learn that he has no available swamps to fetch, which would change his decision. However, I believe he already had access to that information, as his swamp was in his hand, and therefore known to him, and at competitive REL we can reasonably expect players to know their deck's contents. That paragraph's second application might apply to Thoughtseize affecting his decision on what to fetch, but since Mire can only find one target that can cast Thoughtseize in the format, this is also a non-issue.
So, resolve land's ability, in this case being unable to find a swamp. Check, completely legal action. Next: cast thoughtseize with no ability to pay for the spell. Ding ding ding! We've found the point where the sequence breaks down.
If we back up to this point, I believe we damage the game less than if we leave it as is. A backup leaves Astro at 19 life, having essentially missed his first land drop and discarded a card, and Nono with seven (barring mulligans) cards in hand, all of which are known. Not backing up leaves Nono with six cards, and Astro at 17 life. If I'm at the table for this call, I'll back the game up (or, ask the HJ for permission to back it up), issue Astro a warning for GRV, remind both to play more carefully, and move along.
What did I miss? Anything glaringly terrible about this solution/explanation?