o-operate in the formulation of agreed measures, procedures and standards for the implementation of this Convention, with a view to the adoption of protocols and annexes."24
As a matter of fact, the Montreal Protocol of September 1987 had determined the emission levels that different contracting parties should respect and that constitute a directly enforceable legal obligation.25
The Montreal Protocol26 and the two Protocols implementing the 1979 Geneva Convention on Long-Range Transboundary Air Pollution initiated a new method in the development of international regulations that may be called the method of relative standards. According to the Helsinki Protocol of the 1979 Geneva Convention, which provides for the reduction of sulphur emissions: "the Parties shall reduce their national annual sulphur emission or their transboundary fluxes by at least 30 per cent as soon as possible and, at the latest by 1993, using 1980 levels as the basis for calculation of reductions."27
Thus, the obligations accepted by this treaty necessarily vary from one contracting party to the other, since their sulphur emissions in 1980 were not the same. This method seems to be an important innovation in international treaty law.
Difference between the obligations of contracting states may also result from the recognition of the difference between their level of development. The best example of this is Article 5 of the Montreal Protocol on Substances That Deplete the Ozone Layer.28 This provision sets different standards for developing countries than those for industrialized states, but this principle has already been proclaimed in the 1972 Stockholm Declaration.29
The use of umbrella conventions is very frequent in all the new fields where global change has modified international legislative techniques: for example, the international protection of human rights,30 the legal regime of outer space,31 the new Law of the Sea,32 and, of course, environmental protections.33 This means that, a first agreement had to be reached on the principles of common action, while the setting of more precise rules and standards was the aim of the cooperation in the framework that has been created. The fact that international organizations, such as UNEP, play a growing role in the international legislative process is certainly one of the factors that has fostered this development.34
The drafting and the adoption of regional conventions following the same pattern makes it easier to adapt generally agreed upon principles and rules to specific conditions. In the field of the international protection of human rights, this is certainly the case and the regional seas programme of UNEP - which combines it with the technique of umbrella conventions completed by protocol - certainly corresponds to the requirements of realism and efficiency.
More and more often, the drafters of a treaty feel it necessary to provide for an easy updating of the instrument. This is due to the rapid progress in knowledge of the biosphere, its deteriorations, the new forms of pollution, and the new harmful substances that are destroying our planet. The most useful technique in this regard is the adoption of technical norms and specifications -e.g. a list of polluting substances or endangered species- in the form of annexes of the main treaty and of special procedures for modifying such annexes without being obliged to resume the traditional, slow procedure for the modification of treaties.35 This approach shows the intrusion in international law of a new element, the time factor, to which later developments will be devoted.
All these innovations show implications of global change for international law' even if in some cases the use of such new methods and legal techniques started at the end of the 1940s. However, new approaches mostly stem from the necessity to solve international environmental problems. They all seem to be a part of the fundamental changes that international lawyers have to accept. Indeed, they show a trend towards a legal system in which the intricate web of international relat