On September 4, 2026, Malaysia's Sultan Ibrahim Iskandar approved an air quality emergency for Serian, an agricultural town in Sarawak with around 90,000 residents. The Air Pollutant Index (API) there reached 521, far above the threshold of 300, which is already classified as hazardous.
In Kuching, the capital of Sarawak, the figure also reached 311. A day earlier, air pollution in central Singapore briefly entered the unhealthy range for the first time since October 2023.
The cause was a problem that has recurred since the late 1990s: haze from forest and peatland fires in Sumatra and Kalimantan, carried by winds across national borders to Malaysia, Singapore and even central Philippines.
Indonesia's Ministry of Forestry recorded 717 hotspots across the country since early August 2026. Of these, 103 were still active in the 24 hours before the emergency declaration.
The incident has once again raised a familiar question: why does Southeast Asia continue to experience cross-border haze crises almost every year, despite having a regional agreement on the issue since 2002?
The Crisis That Gave Birth to an Agreement
The answer can be traced to the 1997-1998 forest fire crisis, which remains one of the region's worst environmental disasters.
According to reports by the Economy and Environment Partnership for Southeast Asia and the World Wide Fund for Nature, the fires caused around US$1.4 billion in economic losses to Indonesia, Malaysia and Singapore. Broader estimates put the total economic, social and environmental losses across the region at more than US$9 billion.
More than 40,000 people were treated in hospitals for respiratory problems and other illnesses triggered by the haze. The fires were also estimated to have released 1-2 billion tonnes of carbon into the atmosphere.
Pressure from the crisis led the 10 ASEAN member states to sign the ASEAN Agreement on Transboundary Haze Pollution (AATHP) in Kuala Lumpur on June 10, 2002. The agreement came into force on November 25, 2003, 60 days after the sixth country ratified it.
But Indonesia, the country that was the main source of the fires, was the last to ratify the agreement. It did so on September 16, 2014, 12 years after the original signing.
How the Mechanism Actually Works
On paper, the AATHP was designed as a fairly comprehensive framework for regional cooperation. The agreement requires each member state to prevent and monitor forest and peatland fires within its territory. Member states must also exchange information through national monitoring centres and prepare national action plans for peatland management.
In 2007, ASEAN established the ASEAN Transboundary Haze Pollution Control Fund. The joint fund is contributed by member states to support implementation of the agreement and emergency needs.
The most concrete element of this architecture came much later. The founding agreement for the ASEAN Coordinating Centre for Transboundary Haze Pollution Control (ACC THPC) was agreed at the 18th Conference of the Parties to the AATHP in Vientiane, Laos, on August 23, 2023.
The centre was then formally inaugurated by then-ASEAN Chair President Joko Widodo at the ASEAN Summit in Jakarta the following month, 21 years after the original agreement was signed. By the time it launched, only seven of ASEAN's ten member states had signed its founding agreement, though ASEAN has not widely published a detailed list of which countries had yet to do so.
The centre has three main functions: real-time monitoring of hotspots and air quality, coordinating technical assistance between countries, and operating an early warning system to prevent fires from escalating during the dry season.
An Inherent Flaw: The "ASEAN Way" and the Lack of Sanctions
The main problem with the AATHP is not a lack of institutions or mechanisms on paper. The problem lies in how the agreement is enforced, or more precisely, how it is not enforced.
Several academic studies, including a 2026 study by Bagaskara S. Wijaya and Feni F. P. Rozi published in the Journal of Current Southeast Asian Affairs, describe the agreement as an example of soft legalisation. The legal framework is deliberately made politically flexible to respect sovereignty and the principle of non-intervention that characterises the "ASEAN Way".
The study found that ASEAN's institutional practices tend to avoid strong criticism of Indonesia, the country most often identified as a source of haze, in order to maintain regional cohesion.
The weakness is also visible in the text of the agreement. According to an analysis published in the journal International Environmental Agreements: Politics, Law and Economics, many key provisions of the AATHP use loose phrases such as "as appropriate" or "if necessary", without detailed explanations of how they should be implemented, and the agreement does not specify legal consequences for countries that fail to meet their obligations.
The non-interference principle underpinning the AATHP, the analysis argues, has instead given Indonesia room to pursue its own interests even where these conflict with the agreement's goals. There are no provisions on state responsibility, cross-border compensation or sanctions for negligent member states.
The consequences can be seen in ASEAN's own targets. The first roadmap, introduced in 2016, aimed for a "Haze-Free ASEAN" by 2020, but that target was not achieved. In August 2023, ASEAN adopted a second roadmap with the same vision. The deadline was moved to 2030.
Where Did the Fines Go?
The weakness of enforcement is not limited to the regional level. A similar problem exists in Indonesia, where most of the hotspots are located.
Indonesian courts have imposed large fines on companies holding concessions where fires occurred. PT Rafi Kamajaya Abadi, for example, was ordered by the Supreme Court in July 2023 to pay Rp920 billion, or around US$61 million, over fires that burned 2,560 hectares of its land in West Kalimantan. The government is still in the process of collecting the fine, including through the possible seizure of assets.
PT Waringin Agro Jaya was found guilty in 2019 over the 2015 fires in South Sumatra and was fined Rp466 billion. However, the company filed for bankruptcy in March 2023 before it could pay the full amount.
A similar pattern occurred with PT Ricky Kurniawan Kertapersada. The company also filed for bankruptcy without listing the state as a creditor, putting its Rp191.8 billion fine at risk of never being paid.
Research by Greenpeace Southeast Asia found a broader pattern. The 10 palm oil and pulp companies with the largest areas burned between 2015 and 2018 had rarely faced meaningful administrative or civil sanctions. To date, the Indonesian government has also never revoked a single palm oil plantation business licence because of land fires.
The combination of fines that are difficult to collect and administrative sanctions that are rarely imposed means enforcement continues to face problems, regardless of the regional monitoring system built by ASEAN.
Singapore Goes It Alone. Why Is That Not Enough?
The limitations of enforcing the AATHP have also pushed the country most frequently affected by the haze to take action on its own.
Singapore passed the Transboundary Haze Pollution Act in 2014. The law was explicitly designed to apply extraterritorially and allows Singapore to prosecute companies, including those based in Indonesia, if their activities are proven to have caused haze that polluted Singapore's air.
The law sets fines of up to S$100,000 for each day of pollution, with a maximum of S$2 million per company.
In 2015, Singapore issued legal notices to five Indonesian companies, including Asia Pulp and Paper. It also asked four other companies to put out fires on their land and submit fire prevention plans.
But this approach has its own limitations. The Indonesian government openly described the law as a violation of sovereignty.
So far, there is no record of the legal notices resulting in completed court proceedings with actual payment of fines, largely because of the difficulty of enforcing extraterritorial jurisdiction over companies and assets located entirely in another country without enforcement cooperation from the local government.
In other words, even a more forceful unilateral approach faces the same problem of sovereignty.
The Same Dry Season, the Same Question
Back on the haze crisis in Serian and Kuching in early September 2026, Indonesian police had arrested 112 suspects for land burning across 10 provinces. They were also investigating 167 cases involving around 4,700 hectares of burned land in nine provinces, a response faster than in previous decades.
The Singapore Institute of International Affairs (SIIA), an independent policy think tank that has published an annual Haze Outlook since 2019, had in fact flagged the risk months earlier.
On June 24, 2026, it issued a "Red" rating, only the second since the report began, warning of a high risk of severe transboundary haze covering Indonesia, Singapore, Malaysia and Brunei. August and September were identified as the months at greatest risk because of a combination of El Nino and the Indian Ocean Dipole drying out peatlands.
But arrests of people carrying out the burning and increasingly sophisticated early warning systems have yet to address the same structural problems. The absence of binding sanctions for negligent states, corporate fines that can be avoided through bankruptcy, and the principle of non-intervention mean ASEAN remains institutionally reluctant to put strong pressure on its own member states.
Until these gaps are closed, the target of a "Haze-Free ASEAN by 2030" risks meeting the same fate as the 2020 target that came before it.
