I think I read about this somewhere but cannot find it right now. The question is, can I cancel Khal Drogo's (Core) or Catelyn Tully's (LoW) abilities? Not that it makes sense in the second case but still, can I?

Thank you very much!

eloooooooi said:

As for Khal, I guess you can read some here Banner for the Storm

As far as I remember this has been discussed in other topics and the conclusion was that you can cancel those effects.

However your opponent can trigger them again so it will be pretty useless except if you want to get +2 STR from he Calls It Thinking or get rid of some cards to play Ruled by Decree...

So I understand you can cancel those effects. Thank you both

Well... only effects that specifically says "Cannot be cancelled" cannot.

Let's be perfectly clear here:

Yes - you can cancel the effects.

The cards then never leave the hand of your opponent, so he can trigger them again. Immediately. Even without falling afoul of the "one response per trigger" rule.

So No, it is almost never worth it to cancel them. (Unless you need to waste a cancel effect, such as getting a card out of your hand or using up a "cancel the first effect triggered this phase" passive.)