Mr Natuman resigned last week after receiving a letter from the Speaker of Parliament barring him from entering parliament.
Mr Natuman was given a two year suspended sentence in March after earlier pleading guilty to a charge of conspiracy to pervert the course of justice.
He had no immediate plans to step aside, but the Speaker, Esme Saemon, declared his seat vacant and urged him to seek clarification from the courts.
Like Mr Natuman, Mr Loughman is a member of the Vanua'aku Pati for Tanna.
He was Minister of Education from 2013 to 2015 under Mr Natuman's former government.