New Delhi, (PTI) In a major setback to BJP and the Centre, the Supreme Court today ordered restoration of the Congress government in Arunachal Pradesh, saying the "clock should be turned back", as it quashed all decisions of the Governor that precipitated its fall in January, holding them "violative" of the Constitution.

The apex court's verdict came as a shot in the arm for the Congress, paving the way for the return of its dismissed government headed by Nabam Tuki.

Tuki took charge as Chief Minister at Arunachal Bhavan in Delhi tonight.

The landmark unanimous judgement by a five-judge bench set aside among other things Governor Jyoti Prasad Rajkhowa's message directing the preponing of the session and the manner of holding the proceedings of sixth session of the Assembly scheduled from January 14, 2016, to December 16-18, 2015.

The constitution bench, headed by Justice J S Khehar, ordered that status quo ante as prevailed on December 15, 2015 be restored in Arunachal Pradesh Assembly. "The clock should be turned back," it said.

Attorney General Mukul Rohatgi told PTI after a high- level meeting at Prime Minister Narendra Modi's residence that the judgement has to be implemented and the Governor will take all necessary actions and steps.

Today's verdict is the second major blow for the Centre from the Supreme Court which had only in May ordered a fresh floor test in Uttarakhand Assembly that led to the return of the Congress government headed by Harish Rawat and lifting of the President's Rule imposed on March 27.

Tuki welcomed the verdict, saying he has full faith in the judiciary and that he would act as per the constitutional provisions.

The entire opposition hit out at the Modi government, accusing it of "misuse of power" and "transgression" of constitutional structure while BJP criticised the verdict wondering whether it strengthens or weakens democracy.

Reading out the operative portions of the main judgement, Justice Khehar said the order of the Governor dated December 9, 2015, preponing the session of Legislative Assembly from January 14, 2016, to December 16, 2015, is violative of Article 163 read with Article 174 of the Constitution and as such is liable to be quashed and the same is quashed.

"Secondly, the message of governor directing the manner of conducting the proceedings of the sixth session of Legislative Assembly of Arunachal Pradesh from December 16-18, 2015, is violative of Article 163 read with Article 175 of the Constitution and as such is liable to be quashed and the same is quashed," the bench said.

Thirdly, the bench said "all steps and decisions taken by the Legislative Assembly of Arunachal Pradesh in pursuant to Governor's order of December 9, 2015, are unsustainable and liable to be set aside and as such it is set aside."

Finally, the bench observed, "In view of the decision from one to three, status quo ante as it prevailed on December 15, 2015, is ordered to be restored.