Legal Positivism as explained by HLA Hart does not specifically deal with method of legal interpretation. After all, it is a theory about the law, on why law exists and has authority upon the people. In Hart's view, a rule existing in the society shall be treated as a law when the majority of the people in such society accept the authority of such rule from an internal point of view and the legal officers in such society treat such law as an authoritative source in rendering their decision.
Hans Kelsen, the father of Legal Positivism in the Civil Law tradition, also holds a similar position, albeit in a more normative way, i.e. that the validity of the laws is based on power conferring norms existing in a hierarchical system until we reach the basic norm where we presuppose the authority of such basic norm. Upon reaching the basic norm, Kelsen believes that the acceptance of the community of such basic norm is basically a social fact, something that cannot be explained by legal theory anymore.
Thus, in short, under Legal Positivism, law is a social fact, and to certain extent, it might be just a matter of head count. If most people believe and treat a rule as a law, such rule will eventually be considered as a valid law (of course this is a super simplified version of the theory). This however, brings us to the next question i.e., what's the relationship between Legal Positivism and legal interpretation?
A book titled: "Between Authority and Interpretation" written by Joseph Raz, one of Hart's best students, can give a good hint that a theory on legal authority does not automatically deals with theory on legal interpretation. In fact, to the best of my knowledge, I do not think that legal positivism endorses certain kind of legal interpretation method over another method.
This is the crucial point when we deal with Imam's post. From my reading, the critics to Legal Positivism made by the people in his post seem to be confused because they mix up Legal Positivism with rigid textualism. The idea that judges and lawyers should see beyond the text of the law is not an idea rejected by Legal Positivism.
Hart, which was also a master of the linguistic philosophy, acknowledges that there is a limitation for languages in delivering meaning, namely, there is a penumbra, a condition where confident speaker of the language will have different interpretation of a term. In other words, languages might not be able to convey the full intention of the speaker. And in such case, interpretation would be necessary.
Granted, in Hart's view, legal cases should be divided into two types, the easy cases and the hard cases whereas in easy cases, legal interpretation should be minimum since the judges will only need to apply the relevant law to the particular facts while in hard cases, judges will have more discretion. But even in easy cases, Hart believes that there are instances where judges do not have to apply the rules due to reasons such as justice and morality.
Regarding the above division of easy and hard cases, rather than making a normative argument, I think that Hart is making a practical argument, namely, the division is made based on his assessment of judges practices in the real world.
Most modern legal positivists believe that there is no prima facie moral obligation to obey the law, i.e. that the law does not have the highest power to exchange any moral reasoning that can be used by someone as a reason for action. The authority of the law simply lies in the fact that most of us accept such law as an authoritative source but it does not necessarily mean that we have a primary moral duty to obey the law and disregard any other moral reasoning.
This is consistent, I believe, with Hart's theory that law is a social fact. It is the fact in the real world that will determine how the law will be accepted, implemented and interpreted. Hart's theory of Legal Positivism therefore cannot be expected to endorse certain moral values or method of legal interpretation.
So what is the real problem here? If legal positivism can accept interpretation of legal texts, why are we still seeing people blaming Legal Positivism for the lack of progressive movements in Indonesia legal community?
Two possible explanations can be given here. First, the majority of Indonesian judges might actually believe that the law should be interpreted rigidly. Second, rigid interpretation is only being used to justify judges prior belief on certain moral and social issues. For both cases, further research should be done to know what the judges really think. In the United States, such type of research is common because their legal scholars really want to understand how judges will decide cases and what factors will be considered by them. I don't know though about Indonesia or whether our researchers will walk on the same path.
In any case, given the above explanations, I do not think that Legal Positivism can be blamed for the rigidity of the judges (assuming that is correct). Again, we return to the concept of law as a social fact. Legal Positivism will just say that descriptively, the majority of Indonesian judges adhere to strict textualism. Therefore, we can say that in Indonesia, the use of strict textualism will be considered as an authoritative way of reading the law. That's it. As simple as that.
Whether having strict textualist judges is good or not is a completely different question and I don't think that Legal Positivism would have the answer because it is not in the scope of a descriptive/positive theory to say about something normative such as, whether we ought to have judges who are not strict textualists and who will consider other norms and values in rendering their decision.
For me, the fact that Indonesian judges are strict textualists (again, if the assumption is correct since we need more data) does not have any correlation with Legal Positivism. I mean, I am a supporter of Law and Economics movement, who believe that legal rules should be interpreted in a way that maximize efficiency and the welfare of the society, and at the same time, I am also a Legal Positivist.
Can that actually happen? Being a Legal Positivist and at the same time becoming a supporter of Law and Economics? Why not? The problem is, Law and Economics is not yet a mainstream thought in Indonesian legal community and therefore, I would safely assume that most Indonesian judges would not taking it seriously, or even consider it as a part of valid consideration in deciding cases.
But should I blame Legal Positivism for such problem? Of course not. The only reason why strict textualism can become an authoritative method of interpretation is because most of the judges adhere to such method, not because Legal Positivism imposes a normative criteria that good judges should only use strict textualism in order to become authoritative.
If say, I would be able to convince most Indonesian judges in the future that Law and Economics is the best method of legal interpretation and most of them accept such theory and apply it in their cases, would not it be that from Legal Positivism point of view, Law and Economics becomes an authoritative method of legal interpretation that should be followed by the judges? This shows that any method of legal interpretation can live side by side with Legal Positivism.
I think that blaming Legal Positivism for Indonesian judges behavior is misleading. At the highest level, we are dealing with social facts, not normative issues. Prior to 1970s, Law and Economics was not a mainstream thought in the United States, but after the work of many people including scholars, law schools, and NGOs, it became a mainstream thought and currently holds a strong position in antitrust and corporate law cases (though weaker in the field of contracts and torts). The same thing might happen with the legal progressive movements in Indonesia. The question is, do they have a strong basis to convince our judges and lawyers to convert their belief or they simply don't have what it takes to survive in the field of legal theory? Time will tell.