Sue, you are referring to the first trial when they tried to push trough
a treaty for a constitution, which was signed at October 29 in 2004:
The French and the Dutch people said No to it in 2005, and it was the end of the first ratification process.
In 2007 Mrs Angela Merkel tried to revitalise the treaty and they came up with the socalled Lisabon treaty, which was also called "constitution light" from July 2007, signed in December 2007,(but in reality with even more words and changing some words like f.e. "Foreign Minister" would become "High Representative for Foreign Affairs"),
And the clue: It did not arrive before the French and Dutch voters this time...the Parliament would pass it through without asking them
...the Irish were the only people out of the 27 countries which could decide on the people's level and that is why this NO-vote counts so much!
With it the Lisbon treaty, also "constitution light", is not accepted by the EU members in TOTAL, as for ratification ALL 27 countries have to say YES.
With this result the EU's pillar 2 (Solanas CFSP and sending EU peacekeepers and WEU) and also pillar 3: Justice and Internal Affairs (like EU-anti terror fight, Europol, EU-court in Luxembourg, Cross-border police) are unitl today STILL not accepted legally by the population and by the member states law! So they make laws which they call for the sake of missing legality "guidelines" and "rules" and do as if they would be legally binding, getting even payed for it and not little, and the most member countries play this game and accept this...
The yes to the treaty would make all this legally OK. (and with this rec 666 inmplemented into the EU AND its countries, Solanas voice at the UN and more of the power shift from the memberstates to Solana).
That's the importance of the NO! and that's why they write:
"The rejection of the treaty plunged the bloc into a crisis similar to one that hit the EU after French and Dutch voters torpedoed a planned EU constitution in 2005."
http://www.eubusiness.com/news-eu/1213373839.37/view
Thanks Sue for asking - hope it helps!