SI Police Commissioner declared "undesirable immigrant"
Foreign Affairs and Immigration Minister Patteson Oti made the declaration last Friday. Mr Oti however says he is not ready yet to disclose the reasons for his decision because of the sensitivity of the matter.
However, he says the presence of Mr Castles in Solomon Islands is considered prejudicial to peace, defence, public safety, public order, security and good governance of Solomon Islands.
The minister's formal declaration has been gazetted and all relevant authorities, including Mr Castles has been notified of the decision.
Mr Oti says the power to control the admission and expulsion of aliens is one of essential attributes of national sovereignty and had been used by nations of the world.
The declaration of Mr Castles who is an Australian Citizen as an undesirable person was made under the country's Immigration Act.