2 ==> If breaking the King’s Peace is treasonous, did Catelyn commit treason by either abducting Tyrion or after abducting/arresting Tyrion, by not taking him to Kings Landing to stand trial? 3 ==> Even if it wasn’t treasonous, what would Catelyn’s punishment have been for not taking Tyrion to KL, especially had he been executed thanks to a quick step out the Moondoor? Who would be held accountable? Stark, Tully, Arryn, Catelyn, Lysa… (assume no boars or incest to muddy the KL environment.) TY

2. Arresting Tyrion isn’t a breach of the King’s Peace. Catelyn was very careful to follow the legal forms and would have had dozens of witnesses that she had arrested him for a crime committed in Winterfell and was bringing him there to await trial, as is Eddard Stark’s right as a Lord possessing the right of pits and gallows. 

3. She probably wouldn’t face a penalty, given the ambiguity of royal justice and the right of pit and gallows. Especially without evidence of much in the way of royal courts, there’s not much of a sense that there is a right to be tried in a royal court as opposed to by a lord.