EU: Although the constitutional treaty, like all EU treaties, must be approved by all member states before it can come into force, a No vote next week in France or the Netherlands would not leave the constitution legally dead.
Just as Ireland's No to Nice and Denmark's rejection of Amsterdam did not kill off those two treaties, two No votes next week will not necessarily mean the end of the constitution.
In fact, EU constitutional experts say that all other member states are obliged to continue trying to ratify the constitution by November 2006.
"Having agreed and signed the Constitutional Treaty, the member states are under an obligation under international law to seek ratification of the treaty at the domestic level. Their obligations to their fellow high contracting parties under international law . . . require them not to pretend simply that the Constitutional Treaty does not really exist," according to Prof of European Institutions at the University of Edinburgh, Jo Shaw.
After Ireland's initial No to Nice, the Government decided to hold a second referendum in the hope of achieving a different result.
The French prime minister, Jean-Pierre Raffarin, said this week that France will not hold a second referendum on the constitution but such an option remains available - in theory, at least.
According to the constitution, if at least four-fifths of the member states ratify it by November next year and the others are unable to do so, "the matter will be referred to the European Council" of EU leaders.
Politically, two No votes next week would profoundly damage the constitution's prospects of the treaty coming into force and some European politicians and officials, notably in Britain, believe that continuing the process of ratification in such circumstances would do more harm than good.
None have yet come up with a legally plausible mechanism for halting ratification before each country is given an opportunity to have its say on the constitution.
One option might be for member states such as Britain to contrive parliamentary majorities against ratification, thus avoiding the need to hold referendums they fear would result in a No vote.