THE 2002 Asean Agreement on Transboundary Haze Pollution (ATHP) provides a very good opportunity for an examination of Asean environmental diplomacy vis-à-vis the principle of sovereignty over natural resources, transboundary environmental issues, and flexible engagement approach to the Asean Way of consensus and non-interference in domestic affairs.

ATHP is Asean's response to the recurring Indonesian haze (with a respite during the Covid-19 pandemic) which has been affecting the neighboring countries, specifically Singapore, Malaysia and southern Thailand since 1982, extending to a few islands of the Visayas in the Philippines by 2015 — a result of land-clearing fires for palm and rubber tree plantations and the practice of swidden agriculture, particularly on the peatlands of Indonesia. Only in 2002 did Asean formulate a hard law instrument on the issue, the Asean Agreement on Transboundary Haze Pollution. Although generally applicable to all Asean states, it was formulated to target the Indonesian haze. It took effect in November 2003 with the ratification by nine states. Indonesia did not ratify which rendered the agreement essentially ineffective.