How to resolve illegal targeting that was allowed?

Question

I was recently playing Theros, and the set being new, was not familiar with the cards I was playing. Here is the situation that arose:

I had a Stormbreath Dragon out beating face, when my opponent played Chained to the Rocks, targeting my dragon. I, at the time, have forgotten that my dragon has protection from white (and so can't be targeted by Chained to the Rocks), and allow it to be exiled. A couple turns later, I remember about the protection from white.

What is the correct way to resolve this situation? Would the resolution be different if my dragon had not been exiled and instead enchanted by a card such as Pacifism?

(Note: this took place in a limited pre-release tournament, not in a casual game)

Answer 1

The right answer, regardless of REL, starts with "call a judge."

Consequences to rules violations questions always vary depending on the REL (Rules Enforcement Level) that the event is operating under. Prereleases are held at Regular REL, so the IPG (Infraction Procedure Guide) does not apply there - only at Competitive REL.

There is a guide to judging at Regular REL, which refers to the following for miscellaneous mistakes:

A player makes an in-game error not mentioned above

This will cover the bulk of player errors, and we will usually leave the game as it is. Fix anything that is currently illegal (e.g. an Aura enchanting an illegal permanent or a card in the wrong zone) and continue the game. If the error was caught soon after and rewinding is relatively easy, you may choose to undo all the actions back to the point that the illegal action happened. This can include returning random cards from the hand to the library to undo card draws (though don't shuffle the library if you do this!), and reversing various other actions (such as declaring attackers or blockers). Don't go crazy with this!

At the judge's option, he or she can alter the existing game state to best adjust for the mistake. That same guide also calls out:

Keep in mind that the philosophy or fixes found in other documents (such as the Infraction Procedure Guide) are designed for a stricter environment and should not be applied at a tournament run at Regular REL.

There are a number of other articles published by Wizards about judging at Regular REL - see both http://www.wizards.com/Magic/Magazine/Article.aspx?x=judge/article/20080605a and http://www.wizards.com/magic/magazine/article.aspx?x=judge/article/20101111a.

Answer 2

The correct answer (since this appeared in a tournament setting) is to call a judge as soon as you notice.

The judge is likely to act according to section 2.5 Game Play Error — Game Rule Violation of this pdf: http://www.wizards.com/contentresources/wizards/wpn/main/documents/magic_the_gathering_infraction_procedure_guide_pdf2.pdf

If the error is discovered in a reasonable time frame one possibility outlined is a rollback of the game state.

If the error is not discovered in a reasonable time frame (likely you scenario as a couple turns have passed) the judge can leave the game in its current state after resolving state based actions.

From my interpretation of the pdf, your dragon remains exiled in the Chained to the Rocks example, but in the pacifism example the pacifism would be removed.