Zero, the same as most courts.
Enforcement is a matter for (ordinarily) the Security Council, or, in the case of deadlock, potentially the GA acting under Uniting for Peace. Well, decisions on enforcement; actual enforcement is left to individual UN members, acting on direction of those UN bodies.
Note that enforcement in practice is often a problem, as with the provisional measures adopted against Russia in the Ukraine v. Russia genocide case.
Well, Israel is a treaty signatory. That means an ICJ ruling is executable under Israeli law.
That means jack shit right now. But every action taken hereonforth, by leadership or command or individual soldiers, carries with it the burden of future prosecution.