He is the holder of a Bachelor of Laws degree and a Master of Laws degree (majoring in Public International Law) both from the University of Nairobi, a Diploma in Law from the Kenya School of Law and Certificates in Legislative Drafting from the Institute of Advanced Legal Studies of the University of London, the International Legislative Drafting Institute, New Orleans and the International Law Institute. He is an advocate of the High Court of Kenya and a Certified Public Secretary. He is a member of the Law Society of Kenya, the Institute of Certified Public Secretaries of Kenya, and the Kenyan Section of the International Commission of Jurists, the East African Law Society and the Commonwealth Association of Legislative Counsel. He served as the First Chairperson of the Africa Colloquium of Legal Counsel to Parliaments.

Early in his career, Mr. Nyegenye had a stint as a private legal practitioner and as a law lecturer at a number of institutions of higher learning. Thereafter, he served as Parliamentary Counsel in the Office of the Attorney-General, Programme Officer for the Constitution of Kenya Review Commission and Secretary to the Committee of Eminent Persons on the Review of the Constitution of Kenya and Legislative Drafting Consultant to the Government of Kenya and to a number of other governmental and non-governmental organizations. He has done extensive work on the legislative process and legislative drafting in Kenya and elsewhere in Africa and was part of the team which drafted the Proposed Constitution of Kenya, 2005 and the Constitution of Kenya of 2010. He has had a keen interest in the workings of bicameral legislatures.

Mr. Nyegenye joined the Parliamentary Service in 2007, tasked to establish a legal office in the National Assembly, and served as the Director of Legal Services up to 11th October, 2012 when he was appointed as the Clerk of the Senate of the Parliament of Kenya.