Tensions have erupted in Northern Ireland once again, as U.K. and Irish leaders attempt to preserve a long-standing peace deal in the region.

Violence has plagued the streets of Belfast for the past week and dozens of police officers have been injured amid attacks with petrol bombs, vehicles and rocks.

The renewed unrest comes as Ireland and the U.K. marked the 23rd anniversary of the Good Friday Agreement — a historic truce which brought an end to three decades of sectarian violence.

Now, hostilities have come to a head as leaders scramble to agree on new trade rules between the U.K. and European Union without undermining this agreement. The U.K. – which includes Northern Ireland – left the EU in 2020, whereas the Republic of Ireland remains a member of the union.

The British and Irish prime ministers, as well as Northern Irish lawmakers from across the political divide, have condemned the violence and called for calm.

What is happening now?
Recent rioting on the streets of Belfast has seen primarily Protestant pro-British unionist groups clash with mainly Catholic Irish republicans.

The origins of the protests have been attributed in part to resentment among the British loyalist community at the Northern Ireland Protocol – part of the treaty that saw the U.K. leave the EU.

However, the police’s recent decision not to prosecute senior lawmakers from Irish republican party Sinn Fein for breaking Covid rules, in order to attend the funeral of high-profile former Irish Republican Army member Bobby Storey, has also been cited as lighting the tinderbox.

Paramilitary groups and criminal factions have seized upon the discontent to stoke sectarian violence. Many of those arrested have been minors, some as young as 13, and Northern Irish Children’s Commissioner Koulla Yiasouma has said adults persuading young people to commit violence and vandalism is tantamount to “child abuse.”

Former Irish Prime Minister Bertie Ahern told CNBC Monday that the tensions had been simmering since last year, but said peace commitments from politicians on both sides meant it was unlikely to become a long-term issue.

However, he voiced some concern that the “marching season,” a period of regular marches by Protestant groups between April to August, will be more febrile in the wake of the recent clashes.

The Good Friday Agreement, a pair of accords signed on April 10, 1998, brought an end to nearly three decades of sectarian conflict in Northern Ireland, known as The Troubles.

The fact that both the U.K. and the Republic of Ireland were members of the EU was also important and enabled a blurring of borders between the two.

However, the U.K.’s departure from the EU has been accused of undermining the Good Friday Agreement. It mandates either an “Irish Sea border,” between Northern Ireland and the rest of the U.K., or a “hard border” separating Northern Ireland from the Republic of Ireland, which would enrage Irish nationalists.

The Northern Ireland Protocol creates the former – a distinction between Northern Ireland and the rest of the U.K. – and it’s angered the unionist community, which identify as British.

Prior to winning election, U.K. Prime Minister Boris Johnson swore that no government of his would agree to any deal with the EU that saw a customs border for trade crossing the Irish Sea. However, he reneged on that promise within weeks of taking office, leaving unionists feeling disenfranchised and betrayed by London.

U.K. and EU leaders are continuing to finalize the application of trade rules under the Northern Ireland Protocol, although the Financial Times reported Sunday that both sides were optimistic on progress.

Despite the fact that it is not yet fully implemented, goods arriving into Northern Ireland were subjected to EU customs checks in January for the first time.

Ahern suggested that British and European lawmakers will reach an agreement on the border issue, which has caused trade and supply chain disruption, but that might not be enough to put the genie back in the bottle in the short term.

“The million dollar question is: ‘Will that by itself remove the perception that is now ingrained into loyalists that there still is a border down the Irish Sea, that there is this mystical line down the Irish Sea?’ That’s the bit that worries me,” Ahern said.

How will peace be restored?
Among the common institutions enshrined within the Good Friday Agreement was the British-Irish Intergovernmental Conference. However, Ahern highlighted that the group has not met since the governments of Johnson and Irish Prime Minister Micheal Martin took office.

“I see both the government (in Ireland) and the government of the U.K. saying we must implement the Good Friday Agreement … But the one mechanism that’s in the Agreement that both of them have responsibility for is the British-Irish Intergovernmental Conference, and they haven’t met since either government has been elected,” he said.

British and European leaders are now scrambling to establish a way of implementing the Protocol that placates both sides of Northern Ireland’s sectarian divide.