While the Crown remained indivisible, a British subject was outside the denotation of the term “alien”. However, when the Crown divided, so to speak, the denotation of the term “subject of the Queen” changed. As a result, British subjects no longer owed permanent allegiance to the Queen of Australia and became “aliens” in Australia. The meaning of “aliens” in the Constitution does not turn on whether under the law of another country the person in question owes a duty of allegiance to that country. It turns on whether that person owes a duty of permanent allegiance to the Queen of Australia. This change in the application of the term is the result of a number of significant developments since federation. They include:
(a) the gradual emergence of Australia as an independent, sovereign nation (which arguably culminated with the passage of the Australia Acts 1986 (Cth) and (UK));
(b) the acceptance of the divisibility of the Crown (implicit in the development of the Commonwealth as an association of independent nations);
(c) the creation of a distinct Australian citizenship commencing in 1948 with the passage of the Nationality and Citizenship Act and the British Nationality Act 1948 (UK); and
(d) the acceptance by this Court that the phrase “subject of the Queen” in the Constitution no longer means “subject of the Queen of the United Kingdom” but “subject of the Queen of Australia”.
- Constitution of New South Wales by Anne Twomey. (pg 386) https://books.google.com.au/books?id=KayCZfZwafwC&pg=PA386&lpg=PA386&dq=1886+Isaacson+v+Durant&source=bl&ots=S9_r_ExdeM&sig=ACfU3U1fRSZEyIma_27KxU9U0K7v9gCSZg&hl=en&sa=X&ved=2ahUKEwie29HMqPriAhUSbisKHU9DBQsQ6AEwBHoECAkQAQ#v=onepage&q&f=false