An airborne mutant with the guard skill deals no damage to airborne targets.
Then it follows that wardens would not either.
That is part of why I gave the upped version gets 2 use per turn. That way, one use can buff a warden and the other can ground a flying target...
Wonder how well sky wardens would work out with this...
To be fair, an "airborne mutant with the guard skill" wouldn't show up very often in regular play, so maybe zanz didn't consider that possibility when he programmed the guard skill. In the unlikely event that;
1. zanzarino returns,
2. he wants to make a new update, and
3. something similar to this card is going to be added...
then the discussion as to weather flying wardens can hit flying creatures may become a bit less trivial.
For now, your guess is as good as any.