The question of ‘what is valid law’ is perhaps one of the most important questions for a lawyer. The problem with this question is that it rarely provides clear, concrete answers. Take the example of the upstream-downstream paradox from transboundary rivers where international lawyers are often employed to secure the national interests of states. In these circumstances, the upstream state traditionally advocates for the free utilisation of water within its territory, while the downstream state advocates for the waters full continued flow.  Such conflicting expectations raise the difficult question: how can the upstream-downstream paradox be best managed?
When faced with complex challenges, perhaps the more pressing issue is to better understand the present situation by asking the more preliminary question, ‘how can one improve observations’, as opposed to jumping ahead and asking ‘what can be done’. Admittedly, this reflective mode of analysis does not lead directly to better principles, guidelines or blueprints for action. But what it can do is bring about a shift in attention and sensitivity to issues of concern – and this is accomplished by understanding the manner to which legal processes form part of society in operation.
Significantly, operational is understood here not as a question of what is valid law and its passive unending final answers, but rather the more actively variant question of how the international legal system proceeds in determining the law’s validity? To answer this question, it is necessary to shift our frame of thinking from the subjectivities of personal opinion, and offer instead an analysis which can guarantee at least that one’s observations are ‘correctly false’, (e.g. to investigate what is not true in order to deﬁne legal processes more speciﬁcally). 
This certainty in the analysis can be acquired by examining particular reoccurring patterns within society, which of relevance here, is the law’s foremost reoccurring priority: the priority not so much to end disputes, nor to achieve specific purposes, but rather to create a world of expectations so that state practices can continue to be seen as either lawful or unlawful (otherwise the alternative would lead to absolute uncertainty).
In practice, this functional priority of law is operationalised by the conditional programme, ‘if X then Y’, or more specifically, ‘only if fact X is given, can the decision be made Y is legal or illegal’. The advantage here is that this programme underpinning all legal treaties is that it enables the law to prevent any future facts not accounted for at the time of the agreed treaty from being relevant to the legal/illegal decision. Hence, this is how the law offers states legal security, stabilises their expectations, and pacifies enduring conflicts. 
That said, in the event a treaty agreement produces more problems for one state than another (e.g. think of a water-sharing treaty with fixed water allocations), this does not mean that the law simply legitimises the status quo. Rather, it handles the problem by employing a purposive programme, ‘to decide Y for the purpose of achieving X’. Significantly, X expresses the expectation of goals such as ‘equitable utilisation’, or the ‘balancing of interests’ which are applied irrespective of treaty systems regulatory conditions. The advantage here is that this enables the law to reintroduce uncertainty into the established treaty systems, so as to induce learning pressures upon the relevant actors, and thus facilitate a politics of understanding.
Indeed, it is precisely this dual combination of the law’s conditional and purposive programmes which helps explain the manner to which law regulates conflicting expectations – something, I propose, an operational description can offer conceptual clarity to improve the way we account for law’s regulation of society.