The vote by the City Council in early December has sparked weeks of angry demonstrations. Loyalists who want Northern Ireland to remain part of the United Kingdom have thrown Molotov cocktails at police cars, sent death threats to politicians and attacked Catholic churches.
Ironically, the close vote brings Northern Ireland into line with the rest of Britain, The New York Times reported Friday. The British flag only flies over the Houses of Parliament a few days a year.
But in Northern Ireland -- Ulster to diehard loyalists -- the Union Jack has become a symbol of Protestant domination. In loyalist districts such as the Shankill in Belfast the flag is everywhere.
The 2011 census showed Protestants are losing ground. While 48 percent of the population in Northern Ireland identified themselves as Protestants, that was down 5 percentage points in 10 years, while self-identified Catholics were up 1 percent to 45 percent.
Patricia MacBride, a Catholic whose father was killed during the period of violent turmoil from the late 1960s to 1998 known as The Troubles, suggested the demographic changes are fueling the new violence.
"There was always going to be something that triggered this upheaval," she said. "Increasingly, they feel abandoned by the state whose agents they have been for so long."
The Good Friday agreement that led to the bi-community government in Northern Ireland says the province will remain British as long as that has majority support. For Paul Shaw, owner of the Shankill Band Shop, and other loyalists that is the issue.
"If we lose this one, we'll have a united Ireland in 5 or 10 years, and we won't accept it," he told the Times. "We'll die to defend the flag. If we have to, we'll go back to the graveyards and the jails."