There are 149 states party to the Genocide Convention. Every one of them has the right to call out the genocide in progress in Gaza and report it to the United Nations.
In the event that another state party disputes the claim of genocide — and Israel, the United States and the United Kingdom are all states party — then the International Court of Justice is required to adjudicate on “the responsibility of a State for genocide.”
These are the relevant articles of the genocide convention:
“Article VIII
Any Contracting Party may call upon the competent organs of the United Nations to take such action under the Charter of the United Nations as they consider appropriate for the prevention and suppression of acts of genocide or any of the other acts enumerated in article III.Article IX
Disputes between the Contracting Parties relating to the interpretation, application or fulfilment of the present Convention, including those relating to the responsibility of a State for genocide or for any of the other acts enumerated in article III, shall be submitted to the International Court of Justice at the request of any of the parties to the dispute.”
Note that here “parties to the dispute” means the states disputing the facts of genocide, not the parties to the genocide/conflict. Any single state party is able to invoke the convention.
There is no doubt that Israel’s actions amount to genocide. Numerous international law experts have said so and genocidal intent has been directly expressed by numerous Israeli ministers, generals and public officials.