Edison format ruling
Royal Oppression

Card text as printed in this era① If a monster(s) would be Special Summoned,
or if a card/effect is activated, that could Special Summon a monster(s) when it resolves:
Either player can pay 800 LP;
they negate the activation, and if they do, they destroy it.
Rulings
- You can't activate this card, nor activate its effect, in the Damage Step. (You can't use it to negate Tragoedia, Giant Rat, etc)
- You can activate this card’s effect the moment it is activated (flipped face-up). However, until it has finished resolving, it’s effect can’t be activated again that chain. (For example, if this card is activated (flipped face-up), and the opponent chains "Call of the Haunted" to the activation, this same card’s effect can’t be used to negate that Call of the Haunted, as this card has not finished resolving)
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the Edison forum — sourced change requests get reviewed.