Here's why:
* Dark Bribe's effect: Dark Bribe states: "Destroy 1 monster your opponent controls. If you do, your opponent gains 1000 Life Points."
* Royal Decree's effect: Royal Decree is a Continuous Trap that negates the activation of all Spell/Trap Cards.
* Effect Negation: Royal Decree prevents the activation of any Spell/Trap Cards, including Dark Bribe. Therefore, Dark Bribe cannot activate its effect to destroy Royal Decree.
You need a different strategy to get rid of Royal Decree, such as:
* Cards that destroy Traps: Cards like "Torrential Tribute" or "Heavy Storm" can destroy all Traps on the field.
* Cards that negate Trap effects: Cards like "Solemn Judgment" or "Solemn Strike" can negate the activation of a Trap Card, including Royal Decree.
* Cards that banish Trap Cards: Cards like "Twin Twisters" or "Artifact Lancea" can banish Trap Cards from the field.
Remember, always check the card text carefully to understand how cards interact with each other in Yu-Gi-Oh!