As in the above context of human rights law, the following Chapters 5 and 6 will focus on elements of progressive realisation and non-regression in the context of selected MEA regimes. It will be seen, again, that secondary measures adopted by treaty bodies have played a particularly prominent role in the development of MEA regimes, thus raising the question of their status as law. MEAs further resemble human rights instruments with a view to the sometimes uncertain legal status of ‘soft’ provisions included in treaty language (Section I.). In addition, one may also wonder to what extent IEL has followed the example of human rights law in the development of a subject-specific approach to treaty interpretation that adapts, departs from, or modifies the general framework of the Vienna Convention on the Law of Treaties (Section II.).

THE SOURCES OF INTERNATIONAL ENVIRONMENTAL LAW

It would be most difficult to give a proper account of the current state of development of environmental treaty regimes without considering the whole range of ‘decisions’, ‘recommendations’ or ‘resolutions’ that have been adopted by the decision-making bodies of MEAs. Such measures (again referred to as ‘secondary measures’) usually have in common that they are not expressly accorded a formally binding nature, but are nonetheless used by decisionmaking bodies like the Conferences of the Parties (‘CoP’) to further develop the substance of the agreements, to substantiate ‘open-textured’ treaty provisions, to close gaps within the treaty, and to keep agreements in touch with most recent scientific findings. Secondary measures in this sense differ from other ‘legislative’ measures like the adoption of protocols or appendices to the agreement; the adoption of formally binding amendments to the agreement or appendices thereto; purely ‘internal’ measures that concern the adoption of procedural, financial or organisational rules; or measures that concern the relationship of the agreement with other treaties or organisations. In order to address the legal significance of secondary measures in the present context, an illustrative example may provide useful background (1.), before the problem can be located in the broader context of the sources of international law (2.). As parties have proved quite hesitant to submit to widespread majority decisionmaking, the distinction between secondary measures adopted by ‘unanimity’ or ‘consensus’ (3.), or by majority (4.), retains its importance.