Who administers direct democracy mechanisms at the national level?

Referendum Act 2006www.paclii.org/vu/legis/consol_act/ra120.doc  

Referendum Act PART 2 – PRINCIPAL ELECTORAL OFFICER2. Organisation and administration of elections by the Principal Electoral Officer

(1) The Principal Electoral Officer shall be responsible for the Organisation and administration of elections subject to the powers of the Electoral Commission under the Constitution and this Act.

Vanuatu has a mixed electoral management system: an independent Electoral Commission which oversees a ministerial Electoral Office supervised in turn by a public servant known as the Principal Electoral Officer.