North reaction: Sinn Féin and the DUP have welcomed the French rejection of the proposed EU constitution.
Dublin SF MEP Mary Lou McDonald forecast that the French decision would be followed by other votes to reject the treaty elsewhere in Europe.
She challenged the Government to make clear now what the electorate would be voting for if the planned Irish referendum is carried out in the autumn.
DUP MEP Jim Allister said the vote proved just how out of touch governments could be regarding their electorates and warned against treaty amendments and fresh referendums.
"The people of France have shown great courage and insight in refusing to be browbeaten into a Yes vote by their political elite," he said.
Ms McDonald claimed the two sides in the French vote were not divided over pro- or anti-EU issues.
"This debate is about the future," she said. "It is a debate between those who want to see more powers taken away from national parliaments and given to unaccountable officials and those who want an EU where all member states are treated equally and co-operate in the interests of all."
She characterised the pro-treaty side as seeking an EU which is a "global superpower with its own foreign minister, army and armaments agency".
Mr Allister said the magnitude of the defeat for the constitution could not be overestimated.
"France has always been one of the most pro-European states in the EU," he said. "Yet its people could see the necessity to defend national rights and freedoms against further irreversible transfer of power to unelected Brussels bureaucrats."