Goat format ruling
Royal Oppression

Card effect (current official text)Either player can pay 800 Life Points to negate the Special Summon of a monster(s), and/or an effect that Special Summons a monster(s), and destroy those cards.
Rulings
- There are basically 2 ways to Special Summon a monster. The first way is with a Spell Card like Monster Reborn, a Trap Card like Call of the Haunted, or an Effect Monster like Magical Scientist. The second way is built in to the monster, and Special Summons it without activating an effect, such as Black Luster Soldier - Envoy of the Beginning or Dark Necrofear. Royal Oppression can negate both of these types of Special Summon. In the first case, you chain the activation of Royal Oppression’s effect to the activation of the Spell, Trap, or Monster Card’s effect, and negate the effect. In the second case, right before the monster is Special Summoned, you can activate the effect of Royal Oppression to negate the Special Summon (the same procedure that you use for Horn of Heaven or Solemn Judgment).
- The effects of face-up Trap Cards cannot be activated during the Damage Step, so this card’s effect cannot negate the Special Summoning of a monster by the effect of "Mystic Tomato" or a "Cyber Jar" flipped face-up by an attack.
- You can activate the effect of Royal Oppression as a chain to Monster Gate. No cards will be picked up, and no monster will be Special Summoned (The opponent still must have Tributed a monster as a cost).
- You can activate the effect of Royal Oppression to negate an effect that Summons 1 monster, or Summons multiple monsters (like Cyber Jar, The Shallow Grave, or Valkyrion the Magna Warrior).
- (Search for Royal Oppression 2 to continue reading)
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Goat forum — sourced change requests get reviewed.