The Czech Republic's highest court has endorsed the EU reform treaty, removing the last obstacle to its ratification.
The Czech Constitutional Court on Tuesday ruled that the Lisbon Treaty was in line with the country's constitution, paving the way for Vaclav Klaus, the Czech president, to sign the measure.
The Czech Republic was the only EU member state that had not yet ratified the pact, which needs the consent of all 27 member states to come into force.
Klaus long argued against the Lisbon Treaty, which is aimed at transforming the EU into a more unified body.
He has said the treaty could turn the EU into a super state with little democratic control.
Klaus sought an opt-out from the treaty nearly three weeks ago, after Prague's parliament ratified it, in an attempt to ensure the treaty would not allow ethnic Germans expelled from former Czechoslovakia after the second world war to reclaim their property.
Al Jazeera's Hamish Macdonald, reporting from London, said the Czech endorsement is a "significant" development for the EU.
"It's going to pave the way for some pretty enormous changes," he said.
"Perhaps the most high-profile of which will mean there will now be an EU president, a figurehead that is effectively the chairman of the EU council.
"It will also give the European Union a senior foreign policy position, if you like a foreign minister, that will deal with things like Iran and the nuclear debate, Russia and also Afghanistan."
The EU president, who needs to be elected unanimously, will serve a two-and-a-half-year term, strengthening the current system of a six-month presidency that states hold in turn.