Illegal blocks and rewinding

[ESG]

I'd like to get this outcome confirmed:

The RUG Delver player attacks with a flipped Delver of Secrets. The Mono-Black Reanimator player blocks with Putrid Imp, then dumps his hand to gain threshold and pump the Imp, but this turns on the Imp's "can't block" clause.

I am assuming the game rewinds to the point before Declare Blockers and the discarded cards are returned to the Reanimator player's hand. After reading rule 717, I'm also thinking that if one of those discarded cards was a card that would be reshuffled when reaching the graveyard (maybe Worldspine Wurm), then that card, at least, would not be returned. And no cards would be returned at all if an Emrakul was discarded and the graveyard was shuffled.

Do I have that right?


Here are the relevant sections from the Comprehensive Rules:

509. Declare Blockers Step

509.1. First, the defending player declares blockers. This turn-based action doesn't use the stack. To declare blockers, the defending player follows the steps below, in order. If at any point during the declaration of blockers, the defending player is unable to comply with any of the steps listed below, the declaration is illegal; the game returns to the moment before the declaration (see rule 717, "Handling Illegal Actions").

509.1a The defending player chooses which creatures that he or she controls, if any, will block. The chosen creatures must be untapped. For each of the chosen creatures, the defending player chooses one creature for it to block that's attacking him, her, or a planeswalker he or she controls.

509.1b The defending player checks each creature he or she controls to see whether it's affected by any restrictions (effects that say a creature can't block, or that it can't block unless some condition is met). If any restrictions are being disobeyed, the declaration of blockers is illegal.

A restriction may be created by an evasion ability (a static ability an attacking creature has that restricts what can block it). If an attacking creature gains or loses an evasion ability after a legal block has been declared, it doesn't affect that block. Different evasion abilities are cumulative.

Example: An attacking creature with flying and shadow can’t be blocked by a creature with flying but without shadow.


717. Handling Illegal Actions

717.1. If a player realizes that he or she can’t legally take an action after starting to do so, the entire action is reversed and any payments already made are canceled. No abilities trigger and no effects apply as a result of an undone action. If the action was casting a spell, the spell returns to the zone it came from. The player may also reverse any legal mana abilities activated while making the illegal play, unless mana from them or from any triggered mana abilities they triggered was spent on another mana ability that wasn’t reversed. Players may not reverse actions that moved cards to a library, moved cards from a library to any zone other than the stack, or caused a library to be shuffled.

717.2. When reversing illegal spells and abilities, the player who had priority retains it and may take another action or pass. The player may redo the reversed action in a legal way or take any other action allowed by the rules.

[Tempus]

Well you stated it, the situation is not possible. A Putrid Imp can never be declared as a blocker for a flipped Delver of Secrets without discarding at least 1 card prior to the Declare Blockers Step.

So in this situation the cards are discarded and the Reanimator player may assign different blockers (Rewind to the beginning of the Declare Blockers Step). This because there the illegal action occurred and the discarding would have to happen in the Declare Attackers Step to make Putrid Imp Flying and a legal blocker.

[cdr]

If already legally declared as a blocker, it doesn't matter if a creature later gains "can't block". If it's possible to discard at least one card without gaining threshold, you could discard one card to give the Imp flying, block, and then discard the rest to give it threshold.

717 is talking about a single illegal action, and realizing that it's illegal while in the midst of performing the action. Blocking with a non-flying Putrid Imp is one action, and then each discard is another action. In any case, in a competitive event what you're looking for is the IPG section on Game Rule Violation.

Additional Remedy
If the error was discovered within a time frame in which a player could reasonably be expected to notice the error
and the situation is simple enough to safely back up without too much disruption to the course of the game, the
judge may get permission from the Head Judge to back up the game to the point of the error. Each action taken is
undone until the game reaches the point immediately prior to the error. Cards incorrectly placed in hand are returned
to the location in the zone from which they were moved (if the identity of the incorrectly drawn card is not known to
all players, a random card is returned instead). Once the game is backed up, it continues from that point.

If not caught within a reasonable time frame, or backing up is impossible or sufficiently complex that it could affect
the course of the game, the judge should leave the game state as it is after applying state-based actions and not
attempt any form of partial ‘fix’ – either reverse all actions or none, with the following exceptions:
• If a player made an illegal choice or failed to make a required choice for a permanent on the battlefield, that
player makes a legal choice.
• If a player forgot to draw cards, discard cards, or return cards from their hand to another zone, that player
does so.
• If an object changing zones is put into the wrong zone, the identity of the object was known to all players,
and it is within a turn of the error, put the object in the correct zone.

The determination of whether to back the game up is made by a judge, with the HJ's permission. A sequence of actions involving Worldspine Wurm could be backed up, Emrakul probably not unless the previous state of the graveyard was known.

[ESG]

Interesting. Thanks for the responses, but I'm slightly confused. I realize now that I neglected to mention when I posted the question that the Putrid Imp had flying already from an earlier discard, so it was a legal blocker when entering the Declare Blockers step but then achieved threshold. Without threshold, the Putrid Imp chump blocks the Delver and dies in combat; that's easy to understand.

So, the Delver is considered blocked even if the Imp gains threshold (would this be 509.1b?). And is the Imp removed from combat due to the game checking the "can't block" clause before the damage-dealing step? If so, this seems like a way for the Reanimator player to perma-block a flipped Delver. Would this tactic be legal? If the Imp wouldn't be removed from combat, then it would trade with the Delver.

[H]

So, the Delver is considered blocked even if the Imp gains threshold (would this be 509.1b?). And is the Imp removed from combat due to the game checking the "can't block" clause before the damage-dealing step? If so, this seems like a way for the Reanimator player to perma-block a flipped Delver. Would this tactic be legal? If the Imp wouldn't be removed from combat, then it would trade with the Delver.


If already legally declared as a blocker, it doesn't matter if a creature later gains "can't block". If it's possible to discard at least one card without gaining threshold, you could discard one card to give the Imp flying, block, and then discard the rest to give it threshold.

From my understanding, as long as you achieve threshold after the block is already declared, it's irrelevant that it gains "can't block" because what that really means in game terms is "cannot be assigned as a blocker" but it already is so this does not negate a previous legal action (the PImp was a legal blocker when he was declared).

[cdr]

Yes, that's correct H. "~ can't block" is a restriction on declaring blockers (509.1b), the game doesn't care about it at any other time. An Imp with threshold would trade with a flipped Delver.

[ESG]

Wow, this is amazing. I'm so glad I asked! I intend to be killing some Delvers this way in the future ... Thanks, everyone!