At a comp. REL legacy tournament AP is resolving Doomsday and searches their library and graveyard.

NAP is carefully watching AP and intends to figure out what cards from the graveyard are chosen if any. AP is taking up his library and graveyard and puts all in a big pile to search them together.

We are called over and NAP demands that AP keeps the zones separate so he can observe.

Is AP allowed to do as he did or is he obligated to perform his actions technically correct?
If NAPs claim is sustained, what infraction fits APs actions?

On one hand the two zones are separate and of different type of information and thus should be kept separate.
On the other hand the remainder of both zones is going to be in a revealed zone and free information anyways.

While this is easily in the “corner case” category, it's still a question that has some elements that are worth exploring.

As always, we would start by assuring ourselves that it's an honest mistake - and let's just assume that's the case, here.

Most likely, AP never even considered that it might matter to NAP, which cards are chosen from the graveyard; certainly, NAP probably has an opportunity to make that clear before Doomsday starts to resolve.

Mixing the graveyard and library in that manner is not correct, so it's technically a Game Rule Violation; actually assessing that infraction kind of feels excessive, but it's still what we do (hard to imagine, but perhaps AP has always broken this rule, hoping to gain advantage?), so we give AP the Warning.

And, we try to reconstruct the graveyard as best we can. If NAP is so concerned about which graveyard cards might be chosen, then it's possible they have a pretty good idea of what was there already. We just have to leave it to the collective memories of the two players, get the graveyard as close to its previous contents as we can, and then let AP finish resolving Doomsday correctly.

d:^D