Yasuhiro Okudaira, a founding member of the Article 9 Association for defending the Constitution, died of a heart attack at his home in Tokyo early Monday, the association said Friday. He was 85.

Okudaira was a professor of law at the University of Tokyo and International Christian University in Tokyo before founding the association in 2004 with eight other people to call for blocking attempts to amend the Constitution.

Article 9 is known as the war-renouncing clause of Japan's postwar Constitution.

Okudaira denounced the decision by the Cabinet of Prime Minister Shinzo Abe last year to change the government's interpretation of the Constitution in a way that allows Japan to exercise the right to collective self-defense.

For Japan, having the ability to exercise collective self-defense would allow it to attack forces at war with an ally even if Japan itself is not under attack without breaking the Constitution.

At press conferences and public meetings, he insisted that the Cabinet should not exploit its new interpretation to undermine Article 9 and that the act of reinterpretation amounts to a constitutional amendment.