Competative REL. Adam has a Cavern of Souls naming Merfolk. He casts Waterfront Bouncer using the Cavern and an Island without telling his opponent Nigel it has been Errata'd to a Merfolk. Nigel casts a counterspell and Adam tells him it resolves and waits patiently for Nigel to put his counterspell into the graveyard and continue his turn.

Is Adam guilty of anything and should Nigel get a rewind?

Did Nigel ask for the Oracle of the Bouncer, if Adam used colour mana from the Cavern? Or did he make plays based on assumptions he made?

If nothing was said between the players then Adam has done nothing wrong and Nigel learns to be sure about what's happening before making a play. The game state stays as it is

Originally posted by Nicholas Cummings:

Is Adam guilty of anything

Adam did not make any illegal action, nor he omitted any public information. Nigel never asked about the types of Waterfront Bouncer. Adam cannot lie if asked about the types (not lying about derived information). So no problems here. (MTR 4.1 for public and derived information)

Originally posted by Nicholas Cummings:

should Nigel get a rewind?

They haven't committed any infraction at all, so a rewind should not be made. Cast a Counterspell targeting a spell that cannot be countered isn't illegal, it's kinda sloppy, but not illegal.

Edited Vinicius Quaiato (March 21, 2015 08:22:42 PM)

Just confirming what's been said so far - Adam doesn't have to volunteer that information. Also, re: Cavern of Souls, we've said many times that a player is assumed to be using the 2nd ability unless (a) it's not possible (i.e., the spell isn't of the right type), or (b) they specify they're using the 1st ability.

The short version: Nigel has just learned to confirm assumptions before acting.

d:^D