Why is the Montreal Protocol called a success?

The field: the states' environmental relations — the treaties, the customs, the soft-law (the declarations' principles — Stockholm 1972, Rio 1992, Rio+20, Stockholm+50); the field's youth (the 1970s' birth) and growth (the hundreds of MEAs); the structure's problems: the fragmentation (the regimes' silos), the enforcement's weakness (no environmental world court — the ICJ's occasional role; the compliance committees' soft machinery), the North-South's structural politics.