Responses
You could also just take it that if Blues decides to attack jiwoo again than Kayden can kill him and lady Gestella will not well not intervene since she has nothing to do with him now
But that's a gamble. Even though Kayden always looks after Jiwoo he isn't after him 24/7(as both attempts proved). Letting Blues go is a high risk certainly.
Nothing guarantees that next time there will be a high ranker with him when he goes out. I understand gestella position, she raised blues but he is a threat for now.
Gestella, last time you left him out of the wook he tried to kill Jiwho. What guarantees you he won't do the sam again? That's some weird faith over there