Only States are eligible to appear before the Court in contentious cases. At present, this basically means the 192 United Nations Member States.
The Court has no jurisdiction to deal with applications from individuals, non-governmental organizations, corporations or any other private entity. It cannot provide them with legal counselling or help them in their dealings with the authorities of any State whatever.
However, a State may take up the case of one of its nationals and invoke against another State the wrongs which its national claims to have suffered at the hands of the latter; the dispute then becomes one between States.