JurnalPost.com — On Saturday, September 26, 2026, flight operations at Tjilik Riwut Airport in Palangka Raya, Central Kalimantan, were paralyzed by haze from forest and land fires. Drastically reduced visibility forced several airlines to temporarily suspend operations for passenger safety.
Flight disruptions had actually begun several days earlier. A number of airlines, including Garuda Indonesia and Citilink, decided to suspend flights because visibility conditions failed to meet safety requirements.
The impact of the fires extended beyond Kalimantan. On September 26–27, 2026, haze also blanketed Batam, Riau Islands, thousands of kilometers from the fire-affected areas. The Meteorology, Climatology, and Geophysics Agency (BMKG) recorded visibility around Hang Nadim Airport dropping to between two and three kilometers.
Based on satellite imagery, the spread of smoke reaching the Riau Islands was linked to air mass movement from Kalimantan. This phenomenon illustrates how fires in one region can have impacts far beyond their source.
The situation became increasingly concerning as the number of national hotspots rose again. The Ministry of Forestry recorded 1,532 high-confidence hotspots on September 20, 2026, an increase from 1,323 the previous day.
Most hotspots were detected in Central Kalimantan, followed by South Sumatra and West Kalimantan. However, hotspots are indicators of surface temperature anomalies detected by satellites and do not always represent a single fire event.
Across the border, Sarawak, Malaysia, faced similar issues. On September 23, the Air Pollutant Index or Air Pollutant Index (API) in Serian reached the very unhealthy category.
This condition prompted Sarawak education authorities to temporarily close 108 schools in the Serian District starting September 24, with learning activities shifted to home-based study.
This series of events shows that the issue of forest and land fires has transcended administrative boundaries and national sovereignty. As smoke moves with the wind, its impact is felt by communities far from the fire source that have no direct involvement in the activities causing the fires.
Diplomacy Amidst the Haze
Interestingly, Malaysia chose to prioritize a diplomatic approach through the ASEAN regional mechanism in responding to the transboundary haze issue.
On August 22, 2026, Malaysian Prime Minister Anwar Ibrahim and Sultan Hassanal Bolkiah of Brunei Darussalam discussed the matter during the 27th Annual Leaders' Consultation or Annual Leaders' Consultation (ALC-27) held in Bandar Seri Begawan.
Both leaders agreed to use the ASEAN mechanism as a channel for handling transboundary haze. Anwar then requested Malaysian Foreign Minister Mohamad Hasan to follow up on the issue through regional diplomatic channels.
This choice can be read as an effort to maintain good relations between countries while providing diplomatic pressure to ensure the haze pollution issue receives collective attention.
On one hand, a multilateral approach allows affected countries to build coordination without immediately sharpening bilateral disputes.
On the other hand, elevating the forest fire issue to the ASEAN level can be understood as a signal that smoke pollution has become a regional problem requiring more serious handling from the source country.
If this issue continues to recur, Indonesia's credibility in fulfilling its obligations to protect the environment across borders could face international scrutiny.
Meanwhile, technical cooperation has also begun to show progress.
In mid-September 2026, the Chargé d'Affaires ad interim of the Malaysian Embassy in Jakarta, Farzamie Sarkawi, stated that Indonesia had granted approval for Malaysia to conduct weather modification operations through cloud seeding in the border regions of both countries.
According to the statement, the coordination was carried out as part of efforts to reduce the impact of forest fires and the spread of smoke toward Malaysian territory.
Previously, from September 3–5, Malaysia also conducted cloud seeding operations in Sarawak targeting three hydroelectric dams—Batang Ai, Murum, and Bakun—as well as 13 water catchment areas.
The operations in Sarawak aimed to increase water reserves while helping to reduce the impact of the haze. However, domestic operations in Sarawak must be distinguished from the planned or implemented weather modification cooperation at the Indonesia-Malaysia border.
From the perspective of international law, such cooperation has an important foundation through the ASEAN Agreement on Transboundary Haze Pollution (AATHP) 2002.
The agreement regulates the obligations of member states in prevention, monitoring, information exchange, and cooperation in combating forest and land fires that cause transboundary smoke pollution.
Article 12 of the AATHP specifically regulates inter-state assistance in emergencies, including the provision that assistance can only be carried out based on the request or consent of the receiving country.
Meanwhile, Article 27 stipulates that disputes regarding the interpretation, application, or compliance with the agreement shall be settled peacefully through consultation or negotiation.
This provision reflects the The ASEAN Wayapproach, which emphasizes respect for sovereignty, consultation, and consensus.
At a glance, this mechanism seems to provide a way out. Indonesia can accept assistance, Malaysia has room to contribute, and ASEAN provides a coordination framework.
However, the AATHP does not establish a direct sanction mechanism that can be unilaterally imposed on member states deemed not to have fulfilled their obligations.
Therefore, its effectiveness depends heavily on political will, technical cooperation, and the seriousness of each country in carrying out the agreed-upon obligations.
This is where questions regarding sovereignty and state responsibility become important. Who has the authority to authorize cloud seeding operations in Kalimantan's airspace, and to what extent is Indonesia responsible for the impact of smoke crossing national borders?
Questioning Sovereignty and State Responsibility
The first issue relates to the sovereignty of airspace.
Article 1 of the 1944 Chicago Convention asserts that every state has complete and exclusive sovereignty over the airspace above its territory.
This principle is also reflected in Article 5 of Law Number 1 of 2009 concerning Aviation, which states that the Unitary State of the Republic of Indonesia has full and exclusive sovereignty over the airspace of the Republic of Indonesia.
Thus, any flight operation conducted by foreign parties in Indonesian airspace must be subject to applicable legal provisions and permits.
Malaysia does not have the unilateral right to conduct cloud seeding operations in Kalimantan's airspace simply because its national interests are affected by smoke pollution.
If such operations are carried out in Indonesian airspace, approval and technical arrangements from Indonesian authorities are essential elements in determining the legality of their implementation.
On the other hand, granting approval for assistance operations does not mean Indonesia is surrendering part of its sovereignty.
Approval is actually a form of exercising sovereignty, as the state with authority over that airspace retains the right to determine the scope and requirements of permitted activities.
The next issue is state responsibility for transboundary environmental pollution.
In international law, one important case that serves as a reference is the Trail Smelter arbitration between the United States and Canada in 1941.
The case established the principle that a state may not use or permit its territory to be used in a manner that causes serious harm to the territory of another state, if such harm can be convincingly proven.
This principle later developed in international environmental law and is reflected in Principle 21 of the 1972 Stockholm Declaration and Principle 2 of the 1992 Rio Declaration.
Both principles assert that states have the sovereign right to utilize their natural resources but also the responsibility to ensure that activities within their jurisdiction or control do not cause environmental damage in other countries.
In its development, this obligation is linked to the principle of due diligence, which is the obligation of a state to take reasonable and earnest preventive measures in accordance with known risks and its capabilities.
This means international law does not always demand that a state guarantee that fires or pollution will never occur. However, the state is required to carry out prevention, monitoring, and law enforcement obligations adequately.
Difficulties arise when this principle is applied to transboundary smoke pollution.
Proving that haze in a certain area originates from specific hotspots requires scientific data support regarding wind direction, atmospheric conditions, emission source characteristics, and the link between activities suspected of causing pollution and the resulting harm.
Therefore, the existence of transboundary haze is not in itself sufficient to prove that a state has committed a violation of international law.
When State Negligence Must Be Proven
The issue of state responsibility can also be analyzed through the Articles on Responsibility of States for Internationally Wrongful Acts drafted by the International Law Commission (ILC) in 2001.
Article 2 of the document contains two important elements in determining the existence of an internationally wrongful act by a state.
First, the act or omission in question must be attributable to the state under international law.
Second, the act or omission must constitute a breach of an international obligation of the state concerned.
Both elements must be assessed simultaneously.
In the context of forest fires, burning activities carried out by private companies or individuals do not automatically become acts attributable to the state.
However, the state can still be held accountable for its own acts or omissions if it is proven that it did not carry out its international obligations to conduct adequate monitoring and prevention.
In other words, the legal issue does not simply stop at the question of who lit the fire.
The more fundamental question is whether the government has implemented prevention measures, permit oversight, field inspections, and law enforcement in earnest.
This is where Indonesia's domestic policy becomes relevant.
On September 16, 2026, Minister of Forestry Raja Juli Antoni stated that the Ministry of Forestry had frozen the business licenses of 26 companies related to forest fire management.
The freezing is part of administrative sanctions that can be accompanied by environmental restoration obligations and continued to criminal proceedings if criminal elements are found.
A few days later, on September 21, the Ministry of Forestry announced the revocation of licenses for five companies in West Kalimantan, South Kalimantan, and Central Kalimantan.
These steps can be evidence that the state is taking law enforcement actions in handling forest fires.
However, from the perspective of due diligence, the existence of law enforcement actions does not automatically prove that all prevention obligations have been met.
The assessment must still consider when the government became aware of the fire risk, the preventive steps already taken, the effectiveness of oversight, and the response when fires began to occur.
Thus, the policy of taking action against companies is important to consider, but it does not replace the need to test whether the prevention system has been running adequately from the start.
An Umbrella Opened Too Late
In the issue of transboundary environment, the principle of prevention holds a very important position.
The proverb “prepare an umbrella before it rains” is an apt description of how international law should work in facing the risk of environmental pollution.
It is not enough for a state to act only when fires have spread and smoke has reached neighboring territories. Prevention needs to start long before through land monitoring, control of risky activities, and readiness for mitigation.
In this context, the history of Indonesia's involvement in the AATHP is also interesting to observe.
The agreement was signed on June 10, 2002. However, Indonesia only ratified it through Law Number 26 of 2014, about 12 years after signing.
Indonesia became the last ASEAN member state to ratify the agreement.
That delay can be read as one illustration of the political and legal complexity in accepting regional environmental cooperation obligations.
However, the delay in ratification cannot in itself be used as evidence that Indonesia intentionally ignored its responsibility for transboundary smoke pollution.
What is more important to assess is how the obligations in the agreement are implemented after Indonesia officially becomes a party.
The cloud seeding cooperation between Malaysia and Indonesia in 2026 shows that the issue of forest fires cannot be solved only through domestic approaches.
When the impact of fires crosses borders, affected countries need coordination to reduce risks to public health, the environment, and economic activities.
However, such cooperation should not be viewed as a substitute for the government's responsibility in preventing fires from the start.
Weather modification operations are essentially a supporting instrument in mitigation efforts, not a solution that eliminates the need for forest monitoring, land use control, and law enforcement.
Three Layers of Law in Malaysia-Indonesia Cooperation
Ultimately, the legal standing of Malaysia's cooperation in combating Kalimantan's forest fires can be understood through three complementary legal frameworks.
First, the 1944 Chicago Convention and Law Number 1 of 2009 concerning Aviation assert Indonesia's sovereignty over national airspace.
Therefore, the implementation of cloud seeding operations by Malaysia in Indonesian airspace must be based on approval and applicable provisions.
Second, the 2002 AATHP, which Indonesia has ratified through Law Number 26 of 2014, provides a regional cooperation framework to prevent, monitor, and combat transboundary smoke pollution.
Within that framework, technical assistance such as cloud seeding can be a form of cooperation consistent with the agreement's goals, provided it is carried out based on the consent of the receiving country and meets relevant operational requirements.
Third, the principle of state responsibility in international law, including the provisions formulated by the ILC in 2001, provides a framework for assessing whether a state's act or omission can give rise to international liability.
All three have different functions.
Aviation law determines authority over airspace. The AATHP provides a mechanism for pollution mitigation cooperation. Meanwhile, the principle of state responsibility is used to test legal consequences if international obligations are violated.
Thus, cloud seeding cooperation by Malaysia is not inherently contrary to Indonesia's sovereignty. On the contrary, such cooperation can demonstrate that sovereignty and regional solidarity can be exercised simultaneously.
However, the existence of international assistance should also be a reminder that the issue of forest fires requires a stronger commitment to prevention.
Indonesia retains primary responsibility for carrying out environmental protection obligations within its jurisdiction, including through oversight of business activities, action against violations, and restoration of affected areas.
Cooperation with neighboring countries can help reduce the impact of fires, but it does not erase that obligation.
Artificial rain may fall based on consent and cooperation. However, as long as hotspots continue to appear in Kalimantan and smoke continues to move to neighboring countries, the obligation to prevent fires and enforce the law must be carried out consistently.
Smoke may not recognize national borders, but the responsibility to prevent and combat it must not lose its direction.
Sources and References
1944 Chicago Convention on International Civil Aviation, particularly Article 1.
Law Number 1 of 2009 concerning Aviation.
ASEAN Agreement on Transboundary Haze Pollution (AATHP), 2002.
Law Number 26 of 2014 concerning the Ratification of the AATHP.
International Law Commission, Articles on Responsibility of States for Internationally Wrongful Acts, 2001.
Arbitration Trail Smelter between the United States and Canada, 1941 ruling.
1972 Stockholm Declaration and 1992 Rio Declaration.
Ministry of Forestry of the Republic of Indonesia, press release on forest fire control, September 20–22, 2026.
Bernama, reporting on Malaysia–Brunei consultation, August 22, 2026, and Sarawak cloud seeding operation, September 3, 2026.
ANTARA, reporting on Malaysia–Indonesia coordination regarding haze mitigation, September 16, 2026.
ANTARA, reporting on national hotspots and flight disruptions at Tjilik Riwut Airport, September 2026.
Bernama, report on school closures in Serian, Sarawak, September 23, 2026.
BMKG, information on haze distribution in the Riau Islands reported by Batam Pos, September 27, 2026.
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