Just my personal opinion and I know it doesn't count for shit, but I think they should release him.
Sorry, No can do.
Read up on Vienna Convention on Consular Rights.
pakistan is a signatory to this treaty and it clearly "requires the arresting authorities to advise all detained foreign citizens without delay of their right to contact their consulate for assistance."
Article 36 of the VCCR only deals with communication and contact with nationals of the sending state it does not impact convictions for espionage under domestic or international law at all.
Further, Pakistan is a dualist state, wherein any international treaty signed can only be given effect domestically once it has been codified in the corpus of domestic laws through implementing legislation.
Consular access has not been a right explicitly guaranteed under the Diplomatic and Consular Privileges Act, 1972.
Furthermore regarding Geneva Convention IV:
Article 5 of the 1949 Geneva Convention IV provides: “Where in occupied territory an individual protected person is detained as a spy … such … [person] shall nevertheless be treated with humanity, and in case of trial, shall not be deprived of the rights of fair and regular trial prescribed by the present Convention.”
While such a person must, as per Article 5, be treated with humanity and has the right to a fair trial, there is nothing under IHL which prevents an individual from being sentenced to death for espionage.
IHL also draws a clear distinction between those engaged in hostilities and those engaged in espionage. This principle is enshrined in Additional Protocol I (AP I) to the Geneva Conventions, reflecting a long-established principle of international law present in earlier international legal instruments.
Combatants who adhere to IHL principles are, if captured, immune from prosecution for acts committed while engaging in hostilities.
This, however, does not apply to those engaged in espionage: as per Article 46(1) of AP I any member of the armed forces of a party to the conflict who falls into the power of the other party while engaging in espionage shall not have the right to the status of prisoner of war and may be treated as a spy.
Instead, the requirements under Article 75 of AP I are for humane treatment and a fair trial. In this light, therefore,
Pakistan is well within its rights to try and sentence Jadhav under its domestic laws for committing espionage.
While
Jadhav’s activities were hostile acts, inimical to Pakistan’s national security and stability, even if one were to assume that the peacetime regime of international law applied, India’s claims before the ICJ would remain problematic.
India’s declaration to the compulsory jurisdiction of the ICJ under Article 36(2) of the ICJ statute ousts the jurisdiction of the court on matters relating to actions taken in self-defence or in resistance to aggression.
Precedent: Medellin v. Texas
Pakistani Constitution - Third Amendment:
1. Short title and commencement
(1) This act may be called the Constitution (Third Amendment) Act, 1975.
(2) It shall come into force at once.
2. Amendment of Article 10 of the Constitution.
In the Constitution of the Islamic Republic of Pakistan hereinafter referred to as the Constitution, in Article 10-
(a) in clause (4), for the words "one month" twice occurring the words "three months" shall be substituted;
(b) in clause (5), for the words and comma "as soon as may be, but not latter than one week" the words "within fifteen days" shall be substituted; and
(c) in clause (7), in the proviso, after the word "enemy" the commas and words ", or who is acting or attempting to act in a manner prejudicial to the integrity, security of defense of Pakistan or any part thereof or who commits or attempt to commit any act which amounts to an anti-national activity as defined in a Federal Law or is a member of any association which has for its object, or which indulges him, any such anti-national activity" shall be substituted;
3. Amendment of Article 232 of the Constitution.
In the Constitution, in Article 232, in clause (7), for paragraph (b) the following new clause shall be substituted, namely--
"(b) shall, subject to the provisions of paragraph (a) cease to be in force upon a resolution disapproving the proclamation being passed by the votes of the majority of the total membership of the two Houses in joint sitting."
Personally and this is just my opinion and doesn't matter for shit, but I do hope he is spared! 
