@col-klink, Given the witch's track record, I wouldn't be a bit surprised if she executed trees who displeased her. In fact, I think a stone dryad is mentioned in the courtyard of her castle... perhaps if in need of wood she killed them en masse and used the empty shells of their bodies for lumber. 

Also, if the feast scene in PC where the trees break off their fingers to form a bonfire is any clue, perhaps they don't mind donating wood once in a while. (It doesn't seem to hurt them!) Still not sure how they'd feel about contributing whole planks though. Maybe they donate their bodies to a worthy cause in their wills.  

One Narnian no-no (and it might apply to medieval Europe too) is refusing a duel.

@narnianrose 

That's a definitely a big no-no. Glozelle and Sospesian tried to talk to Miraz into refusing the challenge from Peter, but Miraz accepts anyways. Eustace doesn't accept the duel from Reepicheep because he says he doesn't believe in fighting (and of course, that changed after his undragoning).

Posted by: @jasmine_tarkheena

Glozelle and Sospesian tried to talk to Miraz into refusing the challenge from Peter, but Miraz accepts anyways.

Which is what they wanted him to do all along. He starts by talking of refusal for tactical reasons - but they then claim to agree with him and say that for an older man that's a good explanation of why he should refuse, causing him to flare up and wonder whether they think he is a coward.

So tactical considerations during a battle or a war would have been ok, but refusing a challenge because of fear, or for not wanting to fight, would be a no-no.

How about this for a big no-no: preparing the blue fire to call up a dead person!