“I am sad to be leaving; this decision was due to pressure of work,” O’Regan said in a statement.
“The ASA does important work and I wish my successor the best of luck.”
The authority accepted her request to step down as president and chairwoman of the ASA’s final appeal committee after two years in the position.
She took over in 2012 after Prof Mervyn King’s retirement.
“She was a breath of fresh air, in that she not only opened our eyes to things that have always been there which we had not taken care of, but she also focused us on the essence of the existence of the ASA, in particular, speed and accuracy,” ASA chairman Nkwenkwe Nkomo said.
Retired judge Bernard Ngoepe would succeed her. He was Judge President of the High Court in Pretoria as well as chair of the magistrate’s commission.
Ngoepe has previously served as an acting judge of the Constitutional Court.