Catalonia will hold a referendum on independence from Spain on October 1
The announcement on Friday set the stage for months of confrontation with the central government in the capital, Madrid, which says such a vote is illegal and must not take place.
Pro-independence campaigners staged a symbolic ballot, organised by volunteers rather than government officials to get around court restrictions, in 2014, months after Scots voted to stay in the United Kingdom.
Some two million people voted in favour of secession in that non-binding ballot, though turnaround was relatively low.
It is not clear how far the legal wrangling may go this time as the Catalan regional government has said it would throw all its weight behind the vote.
Under the Spanish constitution, referendums on sovereignty must be held nationally, not regionally.
Under Article 155, Madrid has the power to intervene directly in the running of Catalonia’s regional government, forcing it to drop the vote.