I'm going to side with what Andrew said here.

We have something that doesn't conform to a specific infraction, and we have instructions on what to do if we encounter an issue that doesn't conform to a specific infraction, so it seems like we should follow said instructions.

Further noncompliance runs the risk of a USC-Minor.

Originally posted by Eli Meyer:

I actually think you had it right the first time, Sean. Once a player presents their deck, they've effectively stated that they are done sideboarding. Their board is their board, and their deck is their deck. Therefore, this scenario meets the criteria you discussed.

Ahh, but the bit which persuaded me from Andrew is, as Scott Marshall just noted:

Scott Marshall
David, when does a game begin? ;)

And THAT's the key thing here. That's why I'm persuaded by Keeler, but not by Salway: Salway's argument seems to rely to me on the idea that we're in play now, and if that's the case, my argument holds up better to my mind. Keeler's suggests we're not in play, at which point my argument falls down. I accept his argument that we're not in play seems likely, meaning his solution is probably the right one.

Before reading:
So I do not believe that any penalty here applies. It's not D/DLP because this situation does not match anything I can find in the IPG under that section. So I believe the issue here can be put this under a TE that does not have a specific infraction, nor penalty. As per a fix, I do not believe that any of our documentation give us the power to instruct a player to undo a sideboard choice. So no fix, leave as is, and instruct that there is no side boarding between mulligans.

After Reading:
Looks like I'm late to the party and this answer has already been figured out. I need to get to these earlier :).

Originally posted by Jacob Kriner:

Talin Salway
Does the fact that pre-game procedure is part of Tournament Policy override the fact that it is also part of the game rules?

From the Introduction of the MTR:

Excerpt from MTG MTR Intro
Information in this document may contradict (or have information not contained in) the Comprehensive Rules. In such cases, this document takes precedence.

I believe the Pregame Procedure in the MTR will take Precedence over that described in the Comprehensive Rules.

Hmm. That does make sense, though this situation feels like neither a contradiction, nor additional information. It's just the same information, written again.

Would the argument be, then, that -
1) Pre-game procedures are in the CR, but…
2) Pre-game procedures are also in the MTR
3) Therefore, we treat them only as tournament rules, and they are not game rules in a competitive setting.
4) The IPG only has infractions for breaking certain specific tournament rules, not a generic tournament rule
5) Thus, no infraction applies to this situation.

Thanks to everyone who participated this week!

To determine the appropriate infraction, we must first determine which rule
or policy has been violated by Albert's actions. In this case, Albert made
a change to his sideboarding choices during the mulligan process. While
some aspects of the pregame procedure are contained within the
Comprehensive Rules, when a player is allowed to sideboard during a
multi-game match is not one of them. So we know that this isn't a Game Play
Error of any sort.

If this is a violation of the Magic Tournament Rules, we are in the
Tournament Error category. Some have explored the possibility that this
error is covered as a Deck/Deck List Problem. However, we neither have an
illegal deck presented at any point, nor a sideboard change occurring
during a game - we are still in pregame procedures! What this leaves us
with is an uncategorized Tournament Error, for which there is no infraction.

Explain to the players that they may not, in fact, change sideboard
decisions after a mulligan. Ask them to please play more carefully and call
a judge before they take an action they are unsure about, rather than after. Then instruct them
to play on.

Thanks for your contributions this week, and check back very soon for our next scenario!