Magna Carta was one of the most important legal and constitutional documents in history, Ms Adams said.
"For the first time, basic rights were outlined and it was declared that no-one was above the law, including the King.
"It influenced the authors of the United States Constitution and the Universal Declaration of Human Rights and its fundamental guarantee that no-one shall be imprisoned without the lawful judgment of their equals or in accordance with law remains a part of New Zealand law to this day."
The Summit will be attended by international Justice Ministers and Attorneys General, as well as judges, academics, lawyers and business people.
Around 2000 delegates were expected and speakers included Myanmar opposition leader Aung San Suu Kyi, United Kingdom Supreme Court president Lord Neuberger and London Mayor Boris Johnson.