Indian Foreign Minister has termed the detention of Kulbhushan Jadhav as illegal and has asked for his release immediately. https://indianexpress.com/article/india/jaishankar-external-affairs-minister-pakistan-kulbhushan-jadhav-icj-5835581/
After more than 2 years of a legal battle in an international court, India won a legal and diplomatic victory over Pakistan. ICJ ruled that Pakistan must review the death sentence for kulbhushan Jadhav and right to access consular.
And ICJ rejected India's call to the military court decision and ensure his release and safe passage home, ie jadhav will not be free in the immediate effect, it up to Pakistan court now.
India should focus the case will be bring under civilian court as now military court hearing the case.
If case came under civilian court than it will be more transparent and unbiased.
But in real the terrorist outfit jaish ul-adl, linked to the jundaullah, kidnapped Jadhav from Iran and sold him to ISI.