Welcome back to the Knowledge Pool! Today's morsel is Silver, so L2's should quell their ceaseless hunger until after FNM. Good luck, and try not to butcher the truth

Arianna and Neff are playing in a Standard PPTQ. Neff controls Ulamog, The Ceaseless Hunger. Arianna has several cards in her graveyard and 20 cards exiled face-up by Neff's Ulamog. Arianna casts Inverter of Truth. She grabs her deck and says, “My library is exiled and my graveyard will become my library,” to which Neff responds with a nod. Arianna picks up her graveyard and begins shuffling it. After a moment she picks up her old library and says, “Hold on, wanted to check something first,” and begins to look through it. Neff calls for a judge and when you arrive to the table Arianna explains that she wanted to know what she was losing from the Inverter of Truth trigger. What do you do?

I would issue Arianna GPE - LEC - W -looked at cards exiled facedown
Inform her that she does not get to see the cards because they are exiled facedown. No further remedy

I'm going to say it's going to be LEC - W once you exile card's face down, they are not able to be looked at. Unless a specific instruction enables them to do so. There is no remedy to apply, inform arianna to be careful to not do this again.

Upon discussion my Mid-Atlantic Slack #Policy, I believe this is actually a GRV for looking a cards exiled face-down without permission

A player takes an action that may have enabled them to see the faces of cards in a deck that they were not entitled to see.

Keywords here being “in the deck.” Reading the Philosophy section of LEC it says

Once those cards have joined another set, the infraction is handled as a HCE or GRV

therefore this cannot be LEC and must be GRV

This can't be LEC. LEC only applies to cards in the deck. Once they are exiled face down, this is a GRV. Issue a warning to Ariana for GPE-GRV and don't attempt any fixes.

I would rule GPE - GRV, because no other penalty fits and issue a warning. The player needs some educating about those certain rules. Nice scenario!

Yes. This is similar to the Bomat Courier situation that was discussed recently - looking at the face down exiled cards is considered a GRV, Warning as indicated above.

Thanks for chiming in, guys! David Rockwood and Daniel Woolson were quick to point out that this cannot be Looking at Extra Cards because that infraction only applies to looking at cards in a deck. Good catch!

Arianna has committed Game Play Error - Game Rules Violation by looking at face-down exiled cards when she was not allowed to. Instruct Arianna to leave the exiled cards face down and finish the resolution of Inverter of Truth's triggered ability. Neff is not issued a warning for Failure to Maintain Game State because he called attention to Arianna's error at the earliest possible time.

Again, while Arianna's actions may appear to be Looking at Extra Cards, the recent policy update narrows the scope of LEC to cards in a player's deck and no other zone.