How Can Fragmented International Law Tackle Marine Plastic Pollution: Toward an Integrated Global Agreement

When Plastic Enters the Ocean, International Law Remains on the Shore

By 2025, global annual plastic production has climbed to 436 million tons. For every ton of plastic produced, about 75% eventually becomes waste, a significant portion of which enters the ocean through rivers, coastlines, and shipping. Predictive models show that if current production and waste management practices remain unchanged, by 2040, 23 million to 37 million tons of plastic will flow into the ocean each year—equivalent to 50 kilograms of plastic debris accumulating on every meter of coastline worldwide.

This figure has long transcended the realm of environmental issues, becoming a manifestation of global governance failure. Plastic pollution is transboundary, environmentally persistent, and has ecotoxicological effects, yet the response of international law remains a fragmented patchwork of norms. Scientists have detected approximately 190,000 microplastic particles per square kilometer in the South China Sea, found plastic fragments in the digestive tracts of more than 65% of fish in the North Atlantic, and even detected microplastics in human placental tissue. Ecosystems have sounded the alarm, yet international law remains trapped in the gray zone between soft commitments and hard constraints.

The Current International Law Framework: A Loop That Cannot Be Closed

The United Nations Convention on the Law of the Sea (UNCLOS) is regarded as the cornerstone of marine environmental protection. Its Article 194 requires states to take all necessary measures to prevent, reduce, and control marine pollution, and Article 195 prohibits the transfer or transformation of pollution damage into another form. These provisions appear comprehensive, yet they lack specific rules tailored to the particular characteristics of plastic pollution—the persistence of plastics, the fragmentation process, and their capacity for long-distance migration render traditional pollution governance logic ineffective.

More critically, the ambiguity of UNCLOS leads to enforcement uncertainty. Articles 198 through 204 establish notification, cooperation, and monitoring mechanisms, but their implementation is constrained by the funding willingness of developed countries and the capacity gaps of developing countries. The enforcement mechanisms in Articles 213 to 233 rely on coordination among flag states, coastal states, and port states, yet jurisdictional conflicts and a lack of mutual trust between states mean these provisions are rarely activated in practice. The provisions of Article 235 on state responsibility have almost never been applied to plastic pollution cases, due to the difficulty of establishing a causal link between specific pollution sources and environmental damage.

Meanwhile, 17 international instruments—including the London Dumping Convention, the MARPOL Convention, and the OSPAR Regional Convention—each cover a fragment of plastic governance, yet lack a unified normative hierarchy. The London Dumping Convention mainly regulates dumping from ships and aircraft, MARPOL focuses on shipping emissions, and OSPAR, as a regional mechanism, binds only the Northeast Atlantic. These mechanisms overlap with one another but cannot generate synergy. Research indicates that existing international regulations cover less than 30% of the plastic life cycle, leaving land-based source pollution, microplastic control, and the transboundary transfer of plastic waste as typical governance blind spots.

Structural Contradiction: Soft Law Prevails, Hard Law Is Absent

At a deeper level, the predicament of global marine plastic governance stems from two fault lines. First, the international community’s priorities tend toward post-hoc pollution remediation rather than reducing plastic production and use at the source. Second, developed countries export plastic waste to developing countries, causing pollution transfer, but international law lacks effective legal constraints to stop this implicit ecological dumping.

This structural misalignment is reflected at the normative level as “soft law first, hard law absent.” Regional plastic governance practices show two models: one is the EU’s extended supply-chain responsibility model, which emphasizes extended producer responsibility (EPR) and full life-cycle management; the other is the waste-import control model in Southeast and South Asia, based mainly on domestic bans and regional coordination. However, these regional approaches all lack binding standards at the global level. Although the OSPAR Convention has made progress in reducing marine litter, it covers only a single sea area and cannot address transoceanic plastic gyres.

The deeper problem lies in the fragmentation of international environmental law itself. Climate change has the Paris Agreement, and biodiversity has the Kunming-Montreal Global Biodiversity Framework, but plastic pollution did not start the negotiation process for a global plastics treaty until 2022. Even if the negotiations succeed, if the treaty lacks integration mechanisms with existing international law, it may repeat the mistakes of UNCLOS—a grand framework but weak enforcement.

Integrated Framework: Umbrella Convention Plus Thematic Protocols

In response to this fragmentation, academia and policy circles have begun to turn toward more systematic institutional design. The solution proposed by this study is a vertically integrated model of “umbrella convention plus thematic protocols,” supplemented by horizontal institutional linkages.

From the vertical dimension, the Global Plastics Treaty (GPT) should serve as the overarching convention, establishing a global cap on total plastic production and turning the precautionary principle into a “non-regression clause”—that is, countries may not lower existing protection standards on grounds of economic development. The treaty needs to establish a periodic review mechanism to dynamically adjust production quotas based on scientific monitoring data. This should be linked to the carbon market mechanism of the Paris Agreement, creating synergies between plastic reduction and carbon reduction.

From the horizontal dimension, the plastics treaty needs to align with the Basel Convention amendments, strengthening technology transfer and extended producer responsibility for cross-border plastic waste. The plastic waste amendment to the Basel Convention has set a “prior informed consent” threshold for waste trade, but it lacks globally unified technical standards and mutual recognition mechanisms. The study recommends promoting the establishment of a transnational certification system for plastic waste management through mutual recognition of regional standards.

In the area of marine protected areas (MPAs), the BBNJ Agreement (the Agreement on Marine Biodiversity of Areas beyond National Jurisdiction) provides a new legal tool. The study argues that MPA-specific plastic pollution rules should be clarified under the BBNJ framework, including enforceable thresholds—for example, setting an upper limit on microplastic concentrations in protected-area seawater—and a “do no harm” principle prohibiting any maritime activities that could exacerbate plastic pollution.

Compulsory Jurisdiction and Multi-Stakeholder GovernanceIf treaty integration constitutes the institutional skeleton, then enforcement mechanisms are the muscles. The research proposes authorizing the International Tribunal for the Law of the Sea (ITLOS) to exercise compulsory jurisdiction over marine plastic pollution disputes. Though controversial, this idea is not mere fantasy. In a series of advisory opinions in recent years, ITLOS has demonstrated an expansive interpretation of marine environmental obligations; if plastic pollution were brought within its jurisdiction, it could effectively resolve the enforcement blind spots created by the exclusive jurisdiction of flag states.

However, no international mechanism can be divorced from political reality. The research cites China's "Blue Circle" pilot as a case of multi-stakeholder governance. This model brings government, enterprises, communities, and research institutions into a unified collaborative platform, reducing marine plastic waste through digital traceability and market-based incentives. This bottom-up practice offers operational experience for the domestic implementation of global treaties.

Regional Practice and Global Institutional Linkages

Global governance does not mean excluding regional mechanisms. On the contrary, an effective global treaty should accelerate regional experimentation and feed successful experiences back into global norms. Southeast Asia's "Coral Triangle" initiative, the EU's Single-Use Plastics Directive, and Africa's plastic tax policies are all potential institutional testing grounds. The key is to establish a circular feedback mechanism of "regional practice—global standards—regional adjustment."

Ultimately, global governance of marine plastic pollution is essentially an institutional competition over how international law adapts to the ecological era. The old international order was built on the linear logic of state sovereignty and the polluter-pays principle, whereas the plastic crisis demands global life-cycle responsibility, intergenerational equity, and ecological threshold thinking. In this sense, a global plastics treaty is not merely an environmental agreement, but a stress test for international law's evolution from fragmentation toward integration.

Now that microplastics have entered human placentas, the future international legal framework must respond. Not through another ambitious yet hollow declaration, but through a normative system capable of closing governance gaps. Otherwise, the ocean will continue to silently bear the burden of humanity's legal inertia.