PORTADOWN, Northern Ireland — A decision to allow an Orange Order parade through Portadown’s Garvaghy Road brought hundreds of police officers to the area Sunday and exposed a sharp divide between the two main parties in Northern Ireland’s power-sharing government. Residents of the predominantly Catholic neighborhood gathered overnight in pouring rain to block the route. The Parades Commission, which rules on contentious marches, had on Friday approved a reduced version of the parade for Sunday. The route had been barred since 1998, after earlier confrontations led to widespread violence. After a series of legal challenges, Northern Ireland’s senior judge ruled shortly after midnight that courts could not overturn the commission’s independent decision. The commission had rejected more than 1,300 previous requests from the Orange Order to complete the march it was prevented from finishing in 1998. The Police Service of Northern Ireland deployed several hundred officers, with armored vehicles positioned along a narrow lane between the marchers waiting near a church and demonstrators on Garvaghy Road. Police Chief Constable Jon Boutcher said officers would gather video and photographs to identify possible offenses, and urged people to remain peaceful. More than 100 officers from Police Scotland were also sent to Northern Ireland as reinforcements. Sinn Féin, which represents most of Northern Ireland’s Catholic community and is the largest party, stood with the protesters. First Minister Michelle O’Neill told the crowd that Garvaghy Road residents should be able to live without sectarian intimidation. She questioned why the commission had changed course after decades of blocking the march. The Democratic Unionist Party, Northern Ireland’s main pro-British party, backed the Orangemen. Carla Lockhart, the DUP’s MP for Portadown, said the court ruling meant the law supported the parade and accused O’Neill of leading an unlawful protest. The confrontation places pressure on a power-sharing government restored two years ago after a prolonged breakdown linked to disputes over post-Brexit arrangements. The parties’ opposing positions on the march have raised concern that a local dispute could further damage cooperation between them. U.K. Prime Minister Andy Burnham said he would reconsider the commission’s ruling only if Boutcher recommended a change on security grounds. Burnham said preserving the progress made in Northern Ireland was important and called for calm. Northern Ireland Secretary Chris Bryant also said the immediate decisions rested with the police chief. Bryant noted that the Garvaghy Road protest had not been approved by the commission, which requires advance applications for protests against parades. The police chief, meanwhile, said the operation had so far prevented violence or disorder. The Orange Order was founded near Portadown in 1795. Its marches commemorate the 1690 victory of the Protestant King William of Orange, and are viewed by many Catholics as displays of Protestant political power. The dispute over the Garvaghy Road route became a flashpoint in the 1990s, when confrontations surrounding the parade contributed to rioting and killings across Northern Ireland.