Unless he's already fully mind controlled, as soon as he's away from the Evil Princess, he should threaten to resign if he's being reassigned. Accepting the reassignment is a betrayal of both his wife and his political faction. I can only assume the king is being mind controlled too, because it is absolutely stupid to assign ML as a bodyguard for the Evil Princess given the everything in this story (he's a married man and the princess is weirdly obsessed with him which is even shown by her demand to have him assigned to her, he's sworn his allegiance to the prince and while they aren't known to be at odds they're still not allies, the prince and his wife have been facing assassination attempts so assigning his most loyal knight to someone else is outright appalling).