Removing references to the Sovereign (the Queen) and the Governor-General from New Zealand's statute law (legislation written and approved by Parliament) is legally easy to do. All that is required is to pass an enactment which says "All references to the Governor-General, Sovereign and Queen in right of New Zealand should be read as a reference to the President of New Zealand". This is fairly common - when Governor became Governor-General in 1917, all legislation which previously referred to "Governor" was to be read as referring to "Governor-General". This meant that the legislation passed by parliament between 1853 - 1917 did not end up referring to a office that no longer existed. The same goes for references to "the King" prior to the accession of the Queen as Sovereign in 1952.