I attack with Whirling Dervish, which has protection from black, and it is blocked by a white creature. I use Tidal Visionary to make that creature black. Does my Dervish go around the now illegal block?

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    Welcome to the site! I took the liberty of editing your question to add links to the relevant cards and clean it up slightly. I also removed a reference to the card Circle of Protection (COP) since you seemed to be referring to Whirling Dervish's protection from black instead; feel free to make further edits if that's incorrect.
    – Cadence
    Commented May 25, 2022 at 16:13
  • Some related questions: blocked attacker gains flying, blocked attacker gains menace.
    – Cadence
    Commented May 25, 2022 at 16:14

1 Answer 1


The legality of blocks is checked exactly once, during the declare blockers step. Evasion abilities that take effect after that don't matter, as described in comp rule 509.1:

509.1b The defending player checks each creature they control 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.

  • If you also post this answer to Activating an ability that affects blocking after Declare Blockers step, I think we can then start using that one as the canonical question for this. (I think this answer is better than the one already there because it explicitly references 509.1b) Commented May 25, 2022 at 16:24
  • @PhilipKendall Posted. I tried to add some language which makes it clear that it applies to all blocking restrictions and requirements, regardless of how they're phrased, but that's a little trickier since the rules don't call it out the way they do evasion abilities.
    – Cadence
    Commented May 25, 2022 at 17:10
  • This answers the posted question, but it should be noted that in the particular case of protection, the now-[insert attribute here]-creature's combat damage will be prevented by the protection ability.
    – Ben P.
    Commented May 25, 2022 at 17:58

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