What are the prospects that those responsible for war crimes in Gaza will be brought to justice? And might the international criminal court (ICC) achieve its ultimate goal by deterring such crimes in the future?

On Tuesday, the Bar Human Rights Committee urged the ICC prosecutor, Fatou Bensouda, "to initiate a preliminary investigation into crimes being committed in the Gaza Strip". The committee published a letter signed by 20 leading practitioners and academics calling on Bensouda to investigate crimes committed "within the jurisdiction of the ICC".

The authors, all respected QCs or professors, were in no doubt that Bensouda had the necessary jurisdiction to open an investigation under article 15 of the court's Rome statute. They based that on a declaration recognising the ICC's jurisdiction under article 12(3) of the statute, made by the government of Palestine in January 2009. "There is no legal requirement for a further declaration in order for an investigation to be initiated," the lawyers insisted in their letter, which was sent to Bensouda on Sunday.

One international lawyer disagreed. Kevin Jon Heller, professor of criminal law at SOAS, London University, pointed out that the 2009 declaration had been formally rejected by Bensouda's predecessor, Luis Moreno-Ocampo, in April 2012 – a finding glossed over in the letter.

Moreno-Ocampo took more than three years to work out what was wrong with the 2009 declaration. The ICC has jurisdiction over crimes committed in a particular territory only if jurisdiction is granted by the state in whose territory the crimes occurred or by the UN. A state can confer jurisdiction on the court either by becoming a party to the Rome statute or by making a one-off declaration.

Palestine had indeed made such a declaration. But was Palestine a state? Not according to the UN. At the time of Moreno-Ocampo's decision, it was merely an observer at the UN general assembly. So, in the prosecutor's view, Palestine's declaration had no effect.

But the signatories to the letter argued Palestine was granted "non-member observer state status" by the general assembly in November 2012. It was now a state.

Heller argued that the resolution did not have retrospective effect. It did not deem Palestine to have been a state in 2009. So the declaration it lodged then was in effect void.

Of course, there's an easy answer to this. Palestine needs to lodge a new declaration, accepting the ICC's jurisdiction from November 2012. Heller says the new declaration must follow the wording of the old one and refer to acts committed in Gaza or Palestine: it won't be valid if it is limited to acts committed by one side or the other.

By a curious coincidence, the Palestinian foreign minister, Riad al-Malki, went to see Bensouda on Tuesday. Was he in The Hague to lodge a new declaration on behalf of his government? Sadly not. He simply asked for clarification on how a state can accept the jurisdiction of the ICC.

So where does that leave Palestine? It is not a state party to the Rome statute, the ICC said. The court has not "received any official document from Palestine indicating acceptance of ICC jurisdiction or requesting the prosecutor to open an investigation into any alleged crimes" following the resolution granting it non-member observer state status. Therefore, Bensouda said, "the ICC has no jurisdiction over alleged crimes committed on the territory of Palestine".

You would have thought the 20 QCs and professors might have been able to work this out for themselves. Of course, the prosecutor may be wrong and the British lawyers may be right. But it is at best naive and at worst misleading for their letter to give the impression that the matter is beyond any doubt.

They also know that the prosecutor does not launch straight into a formal investigation (which in any event would need prior authorisation by a pre-trial chamber of the court). As she has explained, the first stage is what is called a preliminary examination. This looks not only at whether the court has jurisdiction but also at whether the alleged crimes are being investigated by a country that can bring its own prosecutions. It also considers the interests of justice.

I am sure the British QCs and professors were motivated by the highest humanitarian considerations. In their view, an investigation would "send an unequivocal message to those involved that they stand to be held personally accountable for their actions". They believe it "could play an important role in bringing breaches of international law in the region to a rapid end".

In that case, their way forward is clear. They should be encouraging Palestine to accept the ICC's jurisdiction – something, it seems, Palestinian leaders are now willing to do. That would trigger a preliminary examination and then, perhaps, an investigation into individual responsibilities: the ICC tries individuals, not states. And perhaps then, in the fullness of time, a court might decide just who has been committing war crimes in Gaza.