Protesters demonstrate against the impact of Brexit on the Irish border in Belfast, Northern Ireland | Charles McQuillan/Getty Images Forum It’s time for the DUP to see sense on Brexit There are already areas of policy where Northern Ireland is treated differently from the rest of the UK.

BELFAST — St. Patrick’s Day is a public holiday in Northern Ireland — but everywhere else in the United Kingdom it's business as usual. As March 17 was on Saturday, Northern Ireland’s workers, along with those in the Republic, will get Monday off.

Here is a small example of a difference in rules that the Democratic Unionist Party — which keeps Theresa May's government in power and has an effective veto over Brexit policy — claims undermines the constitutional integrity of the U.K. This bank holiday is regulatory divergence within the British internal market. It is a barrier to trade. Since most businesses in Northern Ireland will be closed, firms in other parts of the U.K. will be unable to transact with them despite it being a normal working day everywhere else.

The DUP wants Northern Ireland to be treated precisely like the rest of the U.K., and they also want the hardest of Brexits. Neither of these aims is complementary to the desire to keep an open border since once Northern Ireland drops out of the European single market and the customs union, goods checking of various kinds becomes inevitable.

In December, the prime minister was ready to sign a deal on "sufficient progress" on Phase 1 of the Brexit talks, only to be dramatically summoned from the negotiating room where she was meeting Jean-Claude Juncker. The DUP then demanded wording be changed to ensure that any measures designed to align Northern Ireland with the Republic (and therefore to the EU) would apply to the whole U.K.

The DUP has consistently pushed for harmonization of Northern Ireland’s corporate tax rate with that of the Republic of Ireland.

Several of the DUP’s Westminster MPs appear to have had a private bet about who could say the most undiplomatic thing about the U.K.’s negotiating partners. Sammy Wilson, the party's Brexit spokesman, described the Irish prime minister as a “nutcase,” and urged U.K. officials to adopt a “no surrender approach,” echoing an ancient Ulster loyalist battle cry.

A border in the Irish Sea

St. Patrick's Day is not the only area where divergence from the rest of the United Kingdom — and convergence with the rest of Ireland — is accepted by the DUP without complaints of imperiled sovereignty.

The island of Ireland is, for example, a single unit for the purposes of animal health control. The DUP has also consistently pushed for harmonization of Northern Ireland’s corporate tax rate with that of the Republic of Ireland, recognizing geography has economic consequences. Last week, presumably with DUP support, the Treasury announced a consultation on possible harmonization of tourism-related taxes with the rest of the island.

None of this is to argue that the DUP should not be forthright in prioritizing the union between Britain and Northern Ireland. That is their founding mission and what their voters expect.

But in calling for flexibility from the EU27 over potential technological solutions (what some term a "smart" border) the DUP has unwittingly drawn attention to how much easier it would be to implement technological solutions at a handful of sea crossings at borders with the rest of the U.K. than at more than 200 land crossings between Northern Ireland and the Republic.

No one can claim no checks exist at present — because of the aforementioned animal health rules, fresh food and agricultural products entering Northern Ireland from Britain are routinely checked already.

Nor, crucially, does the DUP speak for the balance of opinion in Northern Ireland.

It bears repeating that 56 percent of Northern Ireland voted to Remain in the 2016 referendum. Because of Sinn Féin’s policy of abstention from Westminster, and the elimination of more moderate voices at the last general election (in part a consequence of the polarizing effect of Brexit), there is now a solitary non-DUP Northern Ireland MP at Westminster. The party secured just over a third of the vote, but has more than 90 percent of Northern Ireland's representation in the House of Commons. This power is amplified by their deal with May's Conservatives, which allows them more power than any Irish group at Westminster since Charles Stewart Parnell’s Home Rule Party.

It is always difficult to state definitively what consensus opinion in Northern Ireland is — such is the nature of a divided society. And in such societies, crude statements of the majority will tend to do more damage than good: that is why the Good Friday Agreement, and its exquisite power-sharing structures, exists.

Nevertheless, the referendum itself, subsequent elections and polling suggest there is a majority in favor of some form of special arrangement for Northern Ireland — inside the United Kingdom, but with enough alignment to EU rules to prevent a hardening of the border.

Such an arrangement might, in fact, offer a troubled corner of these islands something it has long lacked: strategic advantage. Northern Ireland's business community — courted assiduously by the DUP for years — is increasingly vocal in wanting a solution along these lines.

Your move, DUP

There was much pearl-clutching in London when the European Commission published a draft withdrawal treaty that translated the backstop option outlined in December's "sufficient progress" deal into a structure whereby Northern Ireland would remain in the EU customs and regulatory ambit. It went so far as suggesting joint customs checking by Irish (i.e. EU) and U.K. staff at Northern Ireland borders.

What would the DUP accept instead? What can U.K. negotiators achieve that would satisfy a party that, even more than the Brexit-wing of the Conservative Party, seeks to have its cake while also eating it?

The balance of opinion in Northern Ireland is for an arrangement that is open to both the rest of the U.K., and the rest of Ireland.

The most straightforward solution would be keeping all of the U.K. in the customs union, which would not keep the Irish border frictionless but would certainly help. The DUP continues to work with hard Brexiteers on the Tory backbenches to prevent the government from pursuing this option.

Ireland was partitioned on the basis that a majority in the northeast were not happy with a separatist agenda 100 years ago. The right to self-determination of the people of Northern Ireland is an article of faith for unionism, but the DUP now finds itself in opposition to the majority of Northern Ireland.

A Conservative MEP has called for a second referendum in Northern Ireland on whether the region should remain in the customs union. Such a vote would be risky for a number of reasons. It would likely turn into a proxy border poll on Northern Ireland’s constitutional status. It would also risk further tribalizing a society that has been trying for years to recover from a tribal past.

But it would be most risky for the DUP because in all likelihood they would lose. The balance of opinion in Northern Ireland is for an arrangement that is open to both the rest of the U.K., and the rest of Ireland. If the party refuses to deliver it, they must know they risk the thing they care about most — the union.

The DUP has it in their power to avoid such an outcome.

Matthew O’Toole is the former chief press officer for Brexit in No. 10 Downing Street.