Justice Lokur, who was sworn in by Chief Justice of India S H Kapadia, will continue in office till December 31, 2018.
With this, the strength of the Supreme Court has gone up to 27 as against the sanctioned figure of 31 judges.
Besides striking down the order on sub-quota for minorities within 27 per cent OBC reservation, Justice Lokur recently suspended and ordered the prosecution of Special CBI Judge T Pattabhirama Rao in a corruption case relating to the Karnataka's controversial mining barons Reddy brothers.
The action followed complaints that the judge granted bail to Bellary mining magnate Gali Janardhana Reddy after pocketing a bribe.
Justice Lokur, who earlier served as Chief Justice of Gauhati High Court, was elevated from the Delhi bar as an Additional Judge of Delhi High Court in February 1999.
He continued to be at the Delhi High Court till his transfer to the Northeast in June 24, 2010. Following a 18-month tenure there, Justice Lokur took oath as Chief Justice of Andhra Pradesh High Court on November 15, 2011.