The services of the senior lawyer as AG were terminated by Governor J P Rajkhowa on February 2, soon after imposition of President's Rule in the state on January 26.
However, Thomas, who served as the top law officer of the state during the tenure of Chief Minister Nabam Tuki, sent his resignation letter to newly-elected Chief Minister Pema Khandu on July 26.
"Therefore the withdrawal of pleasure by the Governor to remove the AG and appointing a person of his choice is unsustainable and invalid and against the spirit of Constitution and the judgement of the Supreme Court," he said, adding that the new Chief Minister has the right to choose the new AG of his choice.
In his letter, Thomas said "propriety and tradition demands that on your assuming the office of the Chief Minister, the Council of Ministers headed by you may decide on the appointment of the Advocate General. To facilitate the same, I hereby offer my resignation as AG of Arunachal Pradesh".
The lawyer said the historical apex court verdict, re- installing Congress government in the state, showed that the Governor can act only as per the aid and advice of the Chief Minister and his council of ministers with regard to appointment or termination of services of law officers.
The judgement has made clear that the appointment of the Advocate General and his continuance on his post "during the pleasure of the Governor does not mean his individual pleasure without or other than the advice of the council of ministers headed by the Chief Minister," Thomas said.