Why hydrofluorocarbon rules moved from the climate treaty to the ozone treaty

The Kigali Amendment shifted governance of these non-ozone-depleting gases to the Montreal Protocol, despite objections about its legal authority.

Editorial illustration — not from the study.

Hydrofluorocarbons, or HFCs, were already covered by the UN climate regime, while the Montreal Protocol had experience and institutions suited to regulating them but no clear mandate over substances that do not deplete the ozone layer. The article examines why countries nevertheless pursued the Montreal Protocol as the main venue for HFC governance.

By reconstructing the negotiations behind the Kigali Amendment, the study traces proponents’ motivations, strategies and timing, as well as opposition based on the treaties’ different mandates. It argues that supporters first had to show that the Montreal Protocol was ready to take on the issue before its legal authority could be adjusted.

How HFC rules shifted

The article finds that states can shift an issue between overlapping international regimes when the destination regime has a strong enough practical advantage to outweigh its initial legal limits. In the HFC case, proponents used the Montreal Protocol’s institutions and expertise to build and demonstrate its readiness, then advanced the Kigali Amendment despite objections that HFCs belonged under the UN climate regime. The amendment moved HFC governance from the central climate regime to the ozone-protection regime and shows how states can reshape institutional authority for sector-specific climate action.

Why the treaty shift matters

The case shows that international environmental governance is not fixed entirely by which treaty formally covers an issue. Specialized institutions can become venues for climate mitigation when countries judge that they have useful capabilities, even when their original mandates create legal and political obstacles. The findings help explain how cooperation may develop across overlapping international regimes.

Evidence and limits

This is a legal and political analysis based on a reconstruction of the negotiations leading to the Kigali Amendment. It examines states’ motivations, strategies and sequencing rather than measuring the amendment’s environmental results. The abstract presents the HFC case as an explanation of how institutional authority can shift; it does not establish that the same process will occur in every area of international climate governance.

// Source

International Environmental Agreements Politics Law and Economics · 2026 · DOI: 10.1007/s10784-026-09736-x

View paper (DOI)Open access versionPublished 2026-09-05

Authors: Shiming Yang

Institutions: Leiden University

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