The conspirators were hanged for 'high treason'.
He is guilty of 'treason'.
(..) There can be no doubt now, Queen Elsa is a monster and we are all in grave danger. Prince Hans, Arendelle looks to you. With a heavy heart, I charge Queen Elsa of Arendelle with treason and sentence her to death. Hurry Up! She's dangerous. Move quickly and be careful. The Door not open! (..)2013 Frozen
(..) may be conspiring with a wicked sorceress... to destroy us all? Do not question the Princess. She left me in charge, and I will not hesitate to protect Arendelle from treason. Treason?! Whoa! Whoa! Whoa, boy. Easy. Easy. Princess Anna's horse. What happened to her? Where is she? (..)2013 Frozen