KARLSRUHE, Germany Germany's Constitutional Court on Wednesday began hearing a legal challenge to a planned EU-Canada free trade deal that could paralyze the accord.
Three German activist groups handed in 125,000 signatures to the court in August in opposition to the Comprehensive Economic and Trade Agreement (CETA), which they fear will undermine workers' rights and worsen standards for consumers.
Campact, foodwatch and More Democracy argue CETA breaches Germany's constitution because parts of it can come into force even before national parliaments have had their say.
They want to stop its implementation before official ratification by all EU states.
The court is due to rule on the emergency appeal on Thursday. A ruling in favor of the complaint would make it unlikely that Brussels and Ottawa could sign the accord at a summit on Oct. 27.
Austria's chancellor has expressed strong objections to CETA and said on Monday the court's decision would have a strong influence on whether CETA goes through.
German Economy Minister Sigmar Gabriel last month overcame left-wing resistance in his Social Democrats (SPD) party to CETA. He has said the agreement is the West's chance to shape the rules governing globalization.
Asked what a ruling in favor of the petitioners would mean, he said outside the court: "This would be a catastrophe for Europe."
In a week's time EU trade ministers are due to vote on CETA, which requires unanimous support. The European Parliament would also need to vote to allow it to go into force.
It would also require ratification from national, and some regional, parliaments to go fully into force. A trade agreement with Korea took effect provisionally in 2011 but was not fully ratified until four years later.
"The German government must acknowledge the massive protests and should not approve CETA, even if the mass legal complaint is rejected by the German constitutional court," Katja Kipping, head of the Left party, told the RND newspaper chain.
"CETA accelerates globalization instead of regulating it in a sensible way," Anton Hofreiter, head of the pro-environment Green party in parliament, told RND.
Southern Belgium is set to block the deal, while backing from Slovenia remains uncertain.
Hungary may put the agreement to a parliamentary vote, while Romania has said its support is conditional on Canada agreeing a separate deal to allow visa-free travel.
(Reporting by Ursula Knapp and Caroline Copley; editing by Andrew Roche)