[1] He is the president and co-founder of the Public International Law & Policy Group (PILPG), a Non-Governmental Organization (NGO) which provides pro bono assistance to countries and governments involved in peace negotiations, drafting post-conflict constitutions, and prosecuting war criminals, and was consultant at the London based Bosnian Institute for years.

Williams is regarded as a social entrepreneur for his practical and innovative approach to providing pro bono assistance to clients.

Williams has advised over two dozen governments and parties in Africa, Asia, and Europe including Afghanistan, Bosnia, Iraq, Kosovo, Montenegro and Nagorno-Karabakh as well as the President of Macedonia, President of Estonia, Foreign Minister of Montenegro, and the Foreign Minister of East Timor.

Williams has testified before the U.S. Congress and provided expert commentary in the British House of Commons on peace negotiations.

Prior to his work with PILPG, Williams was representative for the Office of the Legal Adviser at the 45th meeting of the International Whaling Commission.