Ireland has told the UN's top court that states are obliged to co-operate to bring an end to "Israel's serious breach" of its duty to respect the rights of Palestinian people.
Irish Attorney General Rossa Fanning said states are obliged not to render aid or assistance in maintaining this situation.
He said it was Ireland's view that all states are required to review trading relationships with settlements in the Occupied Palestinian Territories, requiring them to take steps to prevent trade which maintains settlement activity or implicitly legitimises Israel's annexation of that territory.
The proceedings follow a December 2022 resolution of the UN General Assembly, meaning they predate the 7 October massacre in Israel and the ensuing hostilities in Gaza.
The assembly has asked the UN's top court to examine the legal consequences of the "ongoing violation by Israel of the right of the Palestinian people to self-determination" due to its prolonged occupation and settlement of Palestinian territories.
"Neither the duration of the occupation nor the scale and extent of settlement activity is, in Ireland's view, justified or permitted by the law regulating the use of force in self-defence"
The case is entirely separate from the one brought before the same court by South Africa, which alleges Israel is responsible for violations of the Genocide Convention as a result of its military campaign in Gaza.
However, it has taken on increased significance in the wake of the current conflict and is likely to increase political pressure on Israel.
Mr Fanning also told the International Court of Justice that Israel's military occupation of the Occupied Palestinian Territories since 1967 has involved extensive, permanent and deliberate settlement building.
He said: "Neither the duration of the occupation nor the scale and extent of settlement activity is, in Ireland's view, justified or permitted by the law regulating the use of force in self-defence.
"Indeed, if the security of one people can only be achieved by the occupation over so many decades of the territory of another people, one has to wonder whether there can be any military solution to the problem that it purports to address. In our view, the only effective solution to the problem can be a political one."
Mr Fanning also told the court that Israel has prevented Palestinian people from exercising their rights to self-determination.
Speaking at the International Court of Justice in The Hague, Mr Fanning said Israel's prolonged occupation of the Occupied Palestinian Territories has "increasingly fragmented Palestinian presence" and use of their land and resources.
"It threatens the viability of a future Palestinian state. The nature, scale and duration of settlement activist is such that its purpose can only be to permanently obstruct the exercise of the Palestinian people's rights to self-determination."
Mr Fanning added: "Ireland has, with regret, concluded that by its prolonged occupation of Palestinian territory and the settlement activities it has conducted there for more than half a century, Israel has committed serious breaches of a number peremptory norms of general international law."
Ireland also told the court that Israel is annexing Palestinian territory in the West Bank.
"In Ireland's view, Israel is already engaged in the process of annexing Palestinian territory. It is doing so de facto through its policy of encouraging demographic change in that territory by population transfer, and by the continuous development and maintenance of permanent settlements and infrastructure.
"Ireland is concerned that it may also be doing so de jure by increasingly extending the application of domestic Israeli law and civilian administration to the settlements in the Occupied Palestinian Territories,, thereby integrating them into its own territory and erasing the differences in law between Israel and the settlements."
Mr Fanning said Israeli settlers had continued to unlawfully destroy and appropriate property throughout the Occupied Palestinian Territories, and that Israel had a policy of encouraging and facilitating the expansion of settlements.
He said this was a clear breach of international law and the Geneva Convention.
Ireland is one of over 50 countries to make submissions in the case concerning Israel's occupation of Palestinian territory.
The hearings at The Hague, which began on Monday, are focusing on Israel's actions over the past several decades.
The General Assembly resolution referred to Israel's "occupation, settlement and annexation" of Palestinian territory since 1967, including measures related to the city of Jerusalem.
Though the nature of Ireland's submission has not yet been disclosed, the Government has long opposed the building of illegal Israeli settlements in Palestinian territory.
Since Israeli prime minister Benjamin Netanyahu took office at the helm of a far right and ultranationalist government in December 2022, there has been a rapid increase in such settlements in the occupied West Bank.
Around 500,000 Israeli settlers now live in the West Bank, which Israeli forces captured in 1967, alongside around 2.7 million Palestinians.
Earlier this week, Palestinian representatives asked the ICJ to declare Israel's occupation of their territory illegal. They argued that such a declaration would help progress a two-state solution, which would establish a Palestinian state alongside Israel.
Riyad al-Maliki, the foreign minister of the West Bank-based Palestinian Authority, told the court that Palestinians had faced decades of discrimination at the hands of Israel.
Several countries have rebuked Israel's actions in occupied Palestinian territory in their submissions and have called on the court to order the unconditional withdrawal of Israeli forces.
South Africa's ambassador to the Netherlands, Vusi Madonsela, told the court that Israel's actions amounted to an "extreme form of apartheid".
But the US told the court yesterday that an immediate withdrawal of Israeli forces could pose security risks for Israel.
"Any movement towards Israel’s withdrawal from the West Bank and Gaza requires consideration for Israel’s very real security needs," Richard Visek, a legal adviser at the US Department of State, said.
Though Israel is not taking part in the hearings, it has rejected the validity of the case and warned in a written submission that interventions by the court could harm the possibility of reaching a two-state settlement.
The hearings, which began on Monday, are scheduled to run until next Monday 26 February.
The 15-judge panel of the ICJ is expected to take several months to reach its conclusions. Rather than a formal judgement, the General Assembly requested a non-binding advisory opinion from the court.
