Easter lilies, the traditional symbol of Irish republicanism, have been banned from Parliament Buildings in Belfast.
The decision was taken after the corporate body of the Stormont Assembly decided that bunches of shamrock should be located inside its halls after objections from unionists.
Sinn Féin protested and immediately threatened legal action.
"If the situation is that the symbols of both traditions can't be treated equally then the logical outcome is to strip the building of any symbols," Mr Dara O'Hagan, the party's representative on the Assembly Commission said.
Unionists claim that the Easter lilies is associated with violent republicanism, particularly with the Provisional IRA.
The emblem is worn on the lapels of republicans every year to mark the anniversary of the 1916 Easter Rising.
Democratic Unionist Mr Jim Wells, who won a vote with the help of the Ulster Unionists, was delighted by the decision.
"I have nothing against shamrocks. I don't think unionists have anything against shamrocks, sure the Queen Mother gives them out on St Patrick's Day.
"We are looking for a symbol that represents nationalism but doesn't represent terrorism," he said.
PA