COUNTY LOUTH, Ireland — The narrow, winding road along the border between counties Armagh and Louth looks like any other in rural Ireland. But there are video cameras on the trees leading to the farm of Thomas “Slab” Murphy, raided by hundreds of police in helicopters two months ago during a crackdown on suspected cross-border fuel laundering.

The area is dotted with monuments to the “disappeared” – killed nearby by the IRA during the “Troubles” in Northern Ireland – another visible sign of how this area requires some of the closest cross-border police co-operation in the EU.

“There have been numerous police raids on [Mr Murphy’s] farm,” says a security source, who spoke on condition of anonymity. “The most recent was about two months ago when 300 police and army from both sides of the border swooped at dawn.”

Tackling criminality in this border area, nicknamed “bandit country” during the Troubles, is at the heart of Irish concerns over British moves to renegotiate its relationship with the EU.

There are fears in Dublin and Belfast that London’s proposal to “opt out” of 130 EU measures dealing with police and judicial co-operation and hold a referendum on EU membership could put lives at risk.

“There are a large number of areas of police and judicial co-operation which could be negatively impacted by such a move,” Alan Shatter, Ireland’s justice minister told the Irish parliament last week.

In his speech, he mentioned the European arrest warrant as critical to fighting terrorism, warning there would be no legal basis for extradition between Britain and Ireland without it. Mutual legal assistance would also be adversely affected, he said.

“It is clear that only the terrorists and criminals will profit from the legal gap,” he said.

Police suspect that Murphy’s farm, which straddles the border between Northern Ireland and the Republic, is involved a fuel smuggling operation costing Dublin and London millions of euro in lost tax. No charges have been made following the raid.

Murphy, 63, has previously faced allegations of being a former IRA leader. He has strenuously denied the allegations.

The threat from dissident Republican terrorists, who operate on both sides of the border, also requires police and customs to use a range of EU justice measures as the legal basis for swapping intelligence information and surrendering suspects.

Security analysts say this co-operation could be jeopardized if British home secretary Theresa May follows through with proposals made public last October to exercise a mass “opt out” and subsequently seek to negotiate with EU partners to opt back into some of these measures.

Britain negotiated the right to withdraw from EU justice and police co-operation measures under the Lisbon treaty, which gives the European Court of Justice the right to make rulings on these matters from December 2014. A final decision by the Conservative and Liberal Democrat coalition on the issue is expected shortly, in order to provide time for London to negotiate with its EU partners.

David Forde, Northern Ireland’s justice minister, wrote this month to the House of Lords warning that Northern Ireland was “particularly vulnerable” to the proposed opt out, given that it was the only part of Britain that shared a land border with another country. His letter, seen by the FT, noted particular concern regarding any British opt out from the European arrest warrant.

Between 2004 and the start of 2013, some 192 suspected criminals or terrorists were surrendered to the British authorities by Ireland under the European arrest warrant, according to Irish figures. Last year, Britain issued 51 warrants to the Irish authorities, of which 14 related to murder, attempted murder, or manslaughter charges. The latest arrest in a terror investigation was made on Friday.

“Police on both sides of the Irish Sea – as well as either side of the border – fear a return to the days when Ireland’s supreme court would refuse extradition of terrorist suspects,” says Hugo Brady, senior research fellow at the Centre for European Reform think tank.

Before the introduction of the European Arrest Warrant, Ireland and Britain relied on the 1957 Council of Europe Convention on Extradition to surrender suspects to its neighbor. But legal experts say this measure is no longer covered by Irish legislation and, in any case, is inadequate for dealing with terrorism.

Lucinda Creighton, Ireland’s Europe minister, said the border situation and the peace process could be complicated by British opt-outs or full withdrawal from the bloc.

“Most worrying is the impact this could have on the delicate peace on the island. We have been able to build the peace process in the context of the EU, which has helped us establish the Good Friday institutions,” she told the FT.

“If we suddenly have a new frontier with UK – and it becomes a new frontier with the EU – this could create issues in terms of border controls.”

— Financial Times