The ICJ only has jurisdiction to hear cases where either (1) the treaty in question explicitly grants it jurisdiction; (2) a state has lodged a declaration with

The ICJ only has jurisdiction to hear cases where either (1) the treaty in question explicitly grants it jurisdiction; (2) a state has lodged a declaration with the ICJ accepting its jurisdiction in general; or (3) the states agree to the ICJ resolving this particular dispute. For NATO, (1) is not applicable-there is no clause in the North Atlantic Treaty granting the ICJ jurisdiction. (3) is very unlikely-if NATO member states decided to expel a member, why would they voluntarily agree to let the expellee challenge the decision in court? For (2), several NATO states - the US is one - have withdrawn their general acceptance of ICJ jurisdiction (or never accepted it to begin with). Even for those who do accept it, the ICJ’s case law says that it cannot hear a case unless all involved states are either subject to, or voluntarily accept, its jurisdiction. It would consider all NATO member states to be involved states, so it could only hear the case if they all consented to it-not happening.