Is the Constitution of Pakistan Positivist in nature, or is it Naturalistic?
It is easy to say it is Naturalistic right off the bat: the Constitution begins by vesting the sovereignty of not just this country, but that of the entire universe in Allah.
The first sentence of the Preamble to the Pakistani Constitution reads:
Whereas sovereignty over the entire Universe belongs to Almighty Allah alone, and the authority to be exercised by the people of Pakistan within the limits prescribed by Him is a sacred trust;
If the above words are to be taken literally, then Pakistan is not a sovereign state, but is rather a trust; this is no doubt a legal absurdity. Pakistan is. in fact, a sovereign country, where a Parliament makes laws.
Pakistan is an Islamic Republic: the term is a unique one.
A Republic is a state in which supreme power is held by the people and their elected representatives, and which has an elected or nominated president rather than a monarch – a sovereign state in its own right.
An Islamic Republic however is a republican government which is governed on the basis of the Laws of Islam.
The Constitution, in its Principles of Policy makes Naturalistic references. Article 37, for example discusses eradication of evil as a state policy, which, is open to Naturalistic interpretations.
Are these sufficient to consider the Constitution as Naturalistic?
I would argue that the Constitution of Pakistan is Positivist.
Pakistan is a sovereign state, with a Parliament that enacted its Constitution, and which can make laws within the limits it set upon itself through the Constitution. Pakistan is an Islamic Republic because the Constitution says so.
The Parliament has unlimited power to amend and modify the Constitution, via the mechanism it has developed in the Constitution. This is reaffirmed by Articles 239 (5) and (6), which state:
Article 239 Constitution Amendment Bill
(5) No amendment of the Constitution shall be called in question in any court on any ground whatsoever.
(6) For the removal of doubt, it is hereby declared that there is no limitation whatever on the power of the Majlis-e-Shoora (Parliament) to amend any of the provisions of the Constitution.
The Constitution makes it abundantly clear that the there is no limitation whatsoever upon the Parliament to amend any portions of the Constitution; no court shall entertain any question regarding the validity of any amendments to the Constitution.
The Parliament can, at least in theory, repeal provisions that make the Constitution look Naturalistic.
Above all, I would argue, the Constitution, created by an Assembly of the elected representatives and can be modified by the Parliament, in itself is a positive law, therefore it not just is Positivist, but should be interpreted this way too.