On February 24, 1976, the treaty was signed into force by the then-leaders of the original members of ASEAN, Lee Kuan Yew, Ferdinand Marcos, Datuk Hussein Onn, Kukrit Pramoj, and Suharto. Other members acceded to it upon or before joining the bloc. It was amended on December 15, 1987 by a protocol to open the document for accession by states outside Southeast Asia, and again on July 25, 1998, to condition such accession on the consent of all member states. On July 23, 2001, the parties established the rules of procedure of the treaty's High Council, which was stipulated in Article 14 of the document. On October 7, 2003, during the annual summit, a declaration was released that says:
"A High Council of [the treaty] shall be the important component in the ASEAN Security Community since it reflects ASEAN’s commitment to resolve all differences, disputes and conflicts peacefully."
China was the first country, followed by India, outside ASEAN to sign the treaty. As of July 2009, sixteen countries outside the bloc have acceded to the treaty. On July 22, 2009, Secretary of State Hillary Rodham Clinton signed the TAC on behalf of the United States. The European Union intends to accede as soon as the treaty is amended to allow for the accession of non-states. The treaty has been endorsed by the General Assembly stating that:
"The purposes and principles of the Treaty of Amity and Cooperation in Southeast Asia and its provisions for the pacific settlement of regional disputes and for regional cooperation in order to achieve peace, amity and friendship among the peoples of Southeast Asia [are] in accordance with the Charter of the United Nations."