The high court in Belfast has thrown out a legal challenge to the Northern Ireland Brexit protocol. The ruling is a setback for the applicants including the Democratic Unionist party and a relief for UK and EU negotiators who are planning to announce a package of new arrangements later on Wednesday aimed at taking the heat out of the dispute over Brexit checks on goods crossing the Irish Sea from Great Britain to Ireland. Mr Justice Colton refused a judicial review, rejecting the argument of the DUP and others that the protocol breached the 1800 Acts of Union, declaring that “much constitutional water has passed under the bridge” since then. Delivering the judgment, Colton agreed with the applicants that the Brexit Withdrawal Act conflicted with the 1800 Acts of Union, but he ruled that the latter legislation including the protocol overrode the provisions of the 200-year old law, as they in effect repealed part of the Acts of Union. He said while the protocol conflicts with the Acts of Union, subsequent treaties – such as the withdrawal agreement with the EU – was a prerogative power over which the courts had little oversight. In a lengthy judgment he went on to dismiss four other grounds for a judicial review. Colton rejected the contention that the post-Brexit trade arrangements breached key provisions of the 1998 Northern Ireland Act that legislated for the peace agreement, concluding that the “focus of all the relevant sections in the agreement and the 1998 act is the choice between remaining part of the UK or become part of a united Ireland” and the peace deal. Significantly, Colton determined that the 1800 Acts of Union and the Brexit withdrawal legislation were both laws of a constitutional character but said his role was to rule on which one should prevail in law. The judge said a starting point, based on fundamental legal principles, was that the most recent legislation should take precedence. He said there was no legal precedent whereby the Acts of Union had operated to “nullify a subsequent act of parliament” but there was capacity for “implied repeal” of statute with the passing of latter laws. Concluding on that issue, he said: “The acts (2018 and 2020 Withdrawal Agreement Acts) have been approved and implemented pursuant to the express will of parliament and any tension with article six of the Acts of Union should be resolved in favour of the agreement acts of 2018 and 2020.” The judicial review proceedings were brought by the former DUP leader Arlene Foster; the former UUP leader Steve Aiken; the Traditional Unionist Voice political leader, Jim Allister; Lord Trimble, the former head of the Ulster Unionist party and co-architect of the 1998 Belfast Good Friday agreement peace deal; the former Brexit party MEP Ben Habib; and the leave campaigner and former Labour MP Kate Hoey. The high court had been asked to decide whether to allow a full-scale judicial review of the law agreed in January 2020 by the EU and the UK as part of Boris Johnson’s “oven-ready” Brexit package put to voters in the 2019 general election. The court said there was “a real issue in relation to the delay” in bringing the case, given the text of the protocol was agreed and published on 19 October 2019 and ratified on 29 January 2020. It said “in those circumstances any challenge should arguably have been brought within three months of the agreement being ratified” but that the case had been brought 15 months later. However, the court said it was the “substance of the challenges” and not the delay that determined its ruling. Habib, one of the applicants, said the detail of the judgment showed the protocol “tramples all over the constitution”. “The prime minister’s proverbial clothes have been removed by this judgment,” he said. “The government must now address how it plans to square its many claims about the integrity of the UK with this union-busting protocol. Not only is the integrity of the union compromised, but so is that of this mendacious administration.”