Here's the relevant part of the Charter.

Charter Amendment 10.2:
(a) No settlement will be captured without an Edict authorising its acquisition in advance.
(b) Captured settlements will be abandoned or given away unless, at the next Diet session, a Charter Amendment incorporates them formally as part of the Reich.
(c) The 33 existing provinces of the Reich are exempt from (a) and (b).
(d) This amendment overrides the constitutional right of Household Armies to conquer one neighbouring province.

My question is, does a vote requiring a two thirds majority automatically take place, or does someone, as Duke Arnold just did, have to propose the amendment?