Joffrey Baratheon

Immune to triggered effects.
Response: After an opponent's character is knelt, pay 1 gold to stand Joffrey Baratheon. Then, he claims 1 power.

Can I use this response when my opponent kneel characters to attack or defend?

That character is knelt so it would be an example of the required state that you can respond to.

Out of curiosity, was there any special reason you though kneeling to attack or defend might not count as an opponent's character being knelt?

Just needed to be sure it doesn't have to be knelt by card effect.