Spain's highest court has upheld a ban on the radical Basque separatist party, Batasuna.
Arnaldo Otegi was the former face of the former party
A spokeswoman for the Constitutional Court said the court had rejected Batasuna's appeal against a lower court ruling last March.
It banned the party for refusing to condemn acts of violence by the armed pro-Basque independence group, ETA.
ETA is alleged to have killed more than 800 people in its 35-year struggle for an independent Basque country.
Spain's Interior Minister Angel Acebes said the ruling was significant.
"As of today, we have completely and definitively eradicated ETA's political party from our democracy to the benefit of the freedom of many and the human rights of all Spaniards," he said.
A spokesman for the Basque Nationalist Party (PNV), in power in the regional Basque Government, said the decision was "logical", AFP news agency reported.
Batasuna's lawyer, Inigo Iruin, said the party would appeal the ruling to the European Court of Human Rights in Strasbourg.
Friday's ruling makes Batasuna the first political party to be banned in Spain since it returned to democracy after the death of dictator General Francisco Franco in 1975.