What is the penalty when a player has forgotten to list battlefields on their decklist at a high-level tournament?

Ruling: At high-level tournaments (high OPL), a player who has forgotten to list battlefields on their decklist should receive a game loss and be required to fix their deck list registration.

Sequences:

• Issue the game loss penalty
• Have the player fix their deck list registration for the next round
• Verify their deckbox contains only 3 battlefields to ensure no additional cards were present

Nuances:

• The timing of when the issue is discovered matters (typically deck checks happen at the start of a round)
• Some people incorrectly suggest treating non-presented battlefields as blank, but there is no rule support for this approach