"As a result of this ruling, I have to assume that ETA has achieved its objectives," said Alfonso Sanchez, 47, who was wounded in a 1985 ETA bomb blast. "All I want is for the law to be enforced and respected, and that we should honor the memory and dignity of the victims."
Prime Minister Mariano Rajoy has called the European court's ruling the worst possible outcome because it will mean that around 100 other prisoners, including convicted terrorists and killers who fall into the same category as Del Rio, will have to be freed.
"I don't like this ruling one bit. I think it is unjust and wrong," Rajoy said.
ETA is considered a terrorist organization by Spain, the U.S. and the European Union. It is blamed for the killings of more than 825 people in a campaign of bombings and shootings aimed at achieving an independent Basque state straddling Spain's border with France.
The group has been decimated by arrests in recent years.