'Policing' compliance --- In the case of trade, for example, it is very hard to know what happens 'beyond the border'. The only way to seek information is through local presence. For example, country X has classified a subsidy it provides as a 'green box', but is that really the case? As long as this 'policing' does not amount to interference, information-gathering seems to be a widely accepted practice.

Source author: Marília Maciel MariliaM@diplomacy.edu