He was never appointed there to hold a position. He was elected and ordered to leave. Call it another name if you want, but he's not a placeholder, just a victim of a crazy Duke with power in his old head accomplishing the laws of his old realm. After all it's a roleplaying game.
That's a reasonable way to see it - honestly, I thought the same at first. Since it seems the Titans think differently, then that clarifies the rule.
The way I see it post-judgment, the issue is not so much that you ordered Eldarion to leave but that you meant to give back the region to the previous Lord - if you had simply hated Eldarion's guts for some random reasons, it would have been OK.
Celine was fast to ensure a punishment, but never to change the law before it as a Judge. Just old things that no one cares until the Titans appears to illuminate our world with a yellow message.
I'm not sure what you mean by that.