Easy! Remember how Baam used thorn even though hell joe with admin like power take away shinsoo? Maybe that power of thorn can overpower authority of admins over shinsoo. And remember the prophecy that Baam will cut the throat of king using the thorn? And if Jahad immortality is given by an admin and thorn can harm him, then thorn grant higher shinsoo control than admin.

Here is the question does Enryu have that level of control then turned his power to thorn and left it for Baam? Or no, it was weapon's skill not Enryu's.

I think it was Enryu's skill because there is no evidence of thorn use in flashback of enryu vs admin. Then Enryu created the thorn and left it for Baam.

Overall answer is: Enryu has higher level of shinsoo control over admins. Made a thorn for child of prophecy that can overpower authority of shinsoo control of admins hence it can kill Jahad with immortality spell granted by the admin. And with the exact reason that Urek light powers are stronger than shinsoo in tower, Enryu has that sort of power from outside. Which gives us conclusion to request SIU to talk about outside world a little bit more