The International Court of Justice (ICJ) began hearing arguments in South Africa’s genocide case against Israel Thursday, setting off the most significant international challenge yet to Israel’s war in Gaza.

Under international humanitarian law, proving allegations of genocide is incredibly difficult. And even if South Africa does prove that Israel is committing genocide — or that it is failing to prosecute incitement to genocide or prevent genocide from occurring — ICJ decisions aren’t necessarily easy to enforce. But these initial arguments aren’t yet entering that complicated territory. Instead, they’re about whether the ICJ will issue a preliminary order for Israel to stop its onslaught in Gaza immediately; the court will rule on that issue after hearing arguments from South Africa and Israel Thursday and Friday. Though Israel could ignore that ruling if it’s issued, it could make Israel’s allies less inclined to support the war.

“This case will provide other states with a basis for pressuring Israel to stop its campaign — it creates a firm and objective historical record which is important in a situation like this where political tensions are so high,” Juliette McIntyre, a lecturer in law at the University of Southern Australia, told Vox.

South Africa’s 84-page application states that “The acts and omissions by Israel complained of by South Africa are genocidal in character because they are intended to bring about the destruction of a substantial part of the Palestinian national, racial and ethnical group,” in violation of the 1948 Convention on the Prevention and Punishment of the Crime of Genocide.

“Genocides are never declared in advance, but this court has the benefit of the past 13 weeks of evidence that shows incontrovertibly a pattern of conduct and related intention,” Adila Hassim, one of the attorneys arguing South Africa’s case, told the judges and crowd assembled at the Peace Palace in the Hague Thursday.

Israel has stridently rejected the filing, calling it a “blood libel” — a reference to a false accusation that originated in the Middle Ages that Jewish people would murder Christians and use their blood in rituals, and which was used as a justification for oppression of Jewish communities.

On Friday, Israel’s legal team responded to South Africa’s arguments by saying the Israeli operations in Gaza were a natural response to the events of October 7, when Palestine Islamic Jihad and Hamas militants attacked Israeli towns and villages, killing around 1,200 people and taking about 240 hostages. As part of its argument, the Israeli team showed video footage and audio from the attacks.

“In terms of the legal arguments, I think that the Israeli lawyers made some significant arguments, but I don’t think that they are going to be sufficient, at this stage of the proceedings” to keep the court from ruling in South Africa’s favor, at least in part, Adil Haque, professor of international law at Rutgers University, told Vox.

“At this stage in the proceedings, South Africa just has to establish that its claims are plausible,” which is a fairly low legal bar, said Haque. South Africa will likely have a more difficult time proving that Israel is committing genocide, is failing to prevent genocide, or is failing to punish incitement to genocide.

In the meantime, Israel’s war in Gaza, the Palestinian enclave ruled by Hamas, continues. Since October, Israel has killed more than 23,000 people, including more than 10,000 children, according to Gaza’s ministry of health; internally displaced 1.9 million; and damaged or destroyed nearly 70 percent of the homes and 50 percent of the buildings in the region.

Why is South Africa bringing charges against Israel?

While South Africa’s filing may not affect the outcome of the war in any meaningful way, it does draw on longstanding ties between Black South Africans’ liberation struggle and that of the Palestinian people. It also signals the country’s desire to challenge the US-dominated international order that it sees as unfair to African and non-Western interests, and does so using an internationally respected body.

It’s significant that South Africa chose to bring charges before the ICJ, especially given the International Criminal Court (ICC) is already investigating alleged war crimes committed by both Israel and Hamas stemming from the October 7 attacks. While the ICC was set up to investigate and prosecute individuals at the highest levels who are accused of planning and directing war crimes, the ICJ exists to peacefully settle disputes between nations. Now, the ICJ proceedings allow South Africa to make a clear statement in an official venue about Israel’s actions in Gaza: that there is international support for Palestinians and that the past three months of relentless bombardments, as well as the denial of access to the necessities of life, is an urgent matter of international concern.

Under the Genocide Convention, any country can bring charges of genocide against another at the ICJ, regardless of whether they are party to the conflict; in 2019, Gambia brought a genocide case against Myanmar due to its crimes against the Rohingya ethnic group, and the ICJ upheld the right of a third, uninvolved state to bring such cases in 2022.

That it’s South Africa — a country with a recent history of racist colonial violence and apartheid — bringing the charges rather than another nation only adds to the gravity of the proceedings.

South Africa’s ruling African National Congress (ANC) has deep ties to the Palestine Liberation Organization (PLO), stretching back to its former leader and South Africa’s first post-apartheid president, Nelson Mandela. The ANC aligned itself with the PLO and other revolutionary causes while Mandela was in prison; after his release, Mandela was a vocal supporter of the PLO and its leader Yasser Arafat, saying in 1990 that “we identify with the PLO because, just like ourselves, they are fighting for the right of self-determination.”

Decades later, that sentiment remains in the South African government, and for many ordinary South Africans who see their struggle against colonialism and apartheid in the Palestinians’ plight and decades-long struggle for self-determination.

“There’s huge historical precedent for it, both in a domestic political context and in a moral [and] legalistic context,” Michael Walsh, visiting scholar at the University of California Berkeley, told Vox. “South Africa has been engaged on the Palestinian issue since really the end of apartheid and the founding of the state. It’s been a prominent issue in South African politics and among South African leaders.”

The ICJ referral is not the first step South Africa has taken to hold Israel to account for its attacks on Gaza; the country has repeatedly condemned Israel’s actions against Palestinians. The parliament also voted to close the Israeli embassy and withdrew its diplomatic staff from Israel, while the foreign ministry delivered a referral to the International Criminal Court to investigate alleged crimes, including the crime of genocide, in the Palestinian territories in November.

Though South African solidarity with the Palestinian cause is a crucial part of its condemnation of Israel, there are domestic and foreign policy reasons to try to hold Israel to account on an international stage — one of those reasons being “legitimacy in the international system and being perceived as a major player,” Walsh said. “I think there’s a perception that South Africa has really fallen in its stature on the international stage.”

That perception is at least partly due to South Africa’s refusal to arrest Sudanese dictator Omar al-Bashir in 2015, when the ousted leader traveled to the country for a meeting of the African Union. The ICC had issued warrants for Bashir’s arrest on charges of war crimes and crimes against humanity in 2009, and on genocide charges in 2010; South Africa, as a party to the ICC, was obligated to arrest Bashir and turn him over to the court for prosecution.

“There’s been lots of pressure put on South Africa over the last couple of years to deal with individuals who have been accused of war crimes but who are clearly not on the Western side of the international political divide,” Walsh said. With the ICJ case, South Africa is able to assert itself as a player on the international stage, express longstanding solidarity with the Palestinian cause, address domestic political sentiments, and point out the imbalance of international bodies when it comes to prosecuting war crimes.

South Africa has a “deep-seated belief that Israel is committing war crimes, and that there’s an important need to hold accountable any state that commits war crimes,” Walsh said. “And I think that they see a tremendous hypocrisy in how war crimes are prosecuted around the world. And so they’ve made this a cause.”

Will the ICJ decision affect the war in Gaza?

It could be months or even years before the ICJ delivers a ruling in the case. And even if the court rules in favor of South Africa, it has little ability to put consequences behind its decisions.

The ICC can prosecute genocide, crimes against humanity, war crimes, and the crime of aggression — for example, Russia’s invasion of Ukraine. And it has the ability to hold people in detention in the Hague until they can serve out their sentence in one of the countries that have agreed to carry out those sentences. The ICJ can’t do any of that. It is primarily a venue for disagreements between states over resources and borders, but there is precedent for hearing genocide cases.

The UN has extremely weak mechanisms for carrying out ICJ rulings; though its decisions are legally binding, countries do disregard them. For example, the ICJ ruled that Russia should immediately end its hostilities in Ukraine; that war is getting ready to enter its third year. The UN Security Council theoretically enforces consequences should a party to the case fail to comply, but one of the five permanent members of that council “can veto any action” the body makes, McIntyre said. The US, which is one of the five permanent members, is a staunch ally of Israel and is unlikely to support a ruling against it.

But the preliminary ruling could also provide a strong diplomatic basis for nations — including the US — to exert pressure on Israel to stop or at least limit the hostilities, McIntyre said. “We have seen some diplomatic language from the US asking Israel to basically tone it down on the military front — this decision could well offer cover and a reason for doing so that is not perceived as backing down against Hamas.”

All that assumes, of course, that the court finds that Israel has to stop fighting as proceedings continue and that it ultimately finds Israel committed genocide. Neither finding is a sure thing.

“The Court could go a lot of different ways in terms of the ordering of provisional measures if they decide to do so,” Zinaida Miller, professor of law and international affairs at Northeastern University, told Vox.

South Africa made the case in its December filing “for broad and urgent measures to be ordered by the Court, including halting military operations and any and all actions that fall within the bounds of the Genocide Convention as well preventing further forced displacement, deprivation of basic necessities like food, water, and medicine, and lack of access to humanitarian aid,” Miller said. That means the ICJ doesn’t have to go as far as calling for a ceasefire; instead, there could be an order for both sides to negotiate a ceasefire, among other alternatives, including approving the remainder of South Africa’s provisional requests: ensuring the prevention of genocide, preventing the destruction of evidence, and allowing adequate humanitarian aid to reach civilians in Gaza.

Accusations of genocide are difficult to prove because they involve not just a state’s actions but intention. Throughout the conflict, pro-Palestinian activists, scholars on the subject, and politicians have accused Israel of genocide — an accusation that’s particularly fraught since Israel was founded in the wake of the Holocaust. But there have been successful prosecutions of genocide — albeit against individuals and not countries — in the 20th century, in Rwanda and Bosnia, via international criminal tribunals set up through the UN.

“The challenge for South Africa will be to demonstrate genocidal intent. Based on the ICJ’s own case law, this is very difficult to establish,” Michael Becker, an assistant professor of international human rights law at Trinity College Dublin, told Vox. “In this case — quite unusually — South Africa will not be limited to reliance on circumstantial or contextual evidence alone. It can also point to a significant number of statements by Israeli government and military officials that arguably provide direct evidence of genocidal intent, although the real meaning and legal significance of these statements will be fiercely contested.”

Another challenge will be determining attribution — what or who represents the state — since the ICJ case is against the state of Israel rather than individuals, as they would be at international tribunals or the ICC.

This case will take months or even years to resolve, but it has already encouraged debate about the role of international law, as well as potentially shifting diplomatic relations and challenging Israel’s treatment of Palestinians in the historical record. But ultimately, though it is an important case, that doesn’t mean an end to the war in Gaza is any closer.

Update, January 12, 4:00 pm ET: This piece, originally published on December 31, 2023, has been updated twice to reflect the start of the proceedings and to expand upon the challenges South Africa may face during the trial.