There is an outstanding ICC warrant for Pressident Omar Hassan al-Bashir's arrest on genocide charges, which he denies.
Thursday's ruling will be closely watched for its possible implications for Bashir and other sitting heads of state as well as for the court itself.
If the ICC rules that South Africa's decision to let Bashir go was an act of non-compliance, the court could then either report Pretoria to the U.N. Security Council or to the ICC's own member states. In either case, South Africa would only likely suffer the diplomatic setback of a court reprimand, rather than any further fine or sanction.
It is also possible that the court may accept South Africa's argument that it was not obliged to implement the warrant.
Pretoria has argued that the ICC's warrant for Bashir's arrest was void in the face of a South African law that grants sitting heads of state immunity from prosecution, in line with customary international law.
However, the ICC's statutes explicitly state that sitting heads of states do not have immunity in war crimes cases.
Bashir, who came to power in Sudan in a 1989 Islamist and military-backed coup, was charged with genocide and crimes against humanity in 2008 over the deaths and persecution of ethnic groups in the Darfur province.
He denies the charges and continues to travel abroad, trailed by human rights activists and shunned by Western diplomats.