A player casts a spell and, before receiving any confirmation from his opponent, starts to resolve the spell. How do we handle this when it creates a judge call?

Does the answer change when:
the spell cannot be easily rewound (ponder)
or provides some kind of advantage even if we rewind the spell (or resolving an enlightened tutor when the top some cards were put there with brainstorm)?
the first instruction on the card involved drawing cards (brainstorm)?
the spell was cast illegally to begin with (didn't pay for thalia)

Originally posted by William Anderson:

A player casts a spell and, before receiving any confirmation from his opponent, starts to resolve the spell. How do we handle this when it creates a judge call?

Does the answer change when:
the spell cannot be easily rewound (ponder)
or provides some kind of advantage even if we rewind the spell (or resolving an enlightened tutor when the top some cards were put there with brainstorm)?
the first instruction on the card involved drawing cards (brainstorm)?
the spell was cast illegally to begin with (didn't pay for thalia)

I think this is multiple questions. There is no one way of handling this.

At Regular REL, if the opponent had no response, it might be as simple as just asking the player to slow down a little. But at Comp, if the spell involved drawing, there could in theory be a GPE DEC game loss. There are then several gradations in between.

Edited Thomas Ralph (June 26, 2013 03:26:29 PM)

It seems that the only difference between these cases and similar cases
where the opponent had a chance to stop the player is that the opponent
would not get a FTMGS penalty.