Based off of the attitude of men of this country, as well as the guards specifically for this part of the story, they think their authority supersedes any other authority, whether it be nobility, royalty, or whatever. I'm not too sure the legal basis for his argument (don't think he really has one) and based off of Ebony's release due to the queen from another country, as well as her guardianship under the Archduke, she exists in a more or less legal grey area. Something akin to diplomatic immunity I'm guessing? Not that this country or many of its inhabitants would recognize it.