"King Juan Carlos was suspected of tax fraud...."
"Interview took place on Mallorca in the early 1990s..."
The ruling means the former monarch could stand trial in Britain.
The former king said he will return frequently to Spain to visit family and friends but will stay in private accommodations.
A Swiss private bank involved in the three-year criminal probe was fined for a reporting failure.
Prosecutors at Spain's Supreme Court have opened several investigations into Juan Carlos' business dealings.
Spain's former king Juan Carlos.
Through his lawyers, he has repeatedly declined to comment on corruption allegations.
While not formally under investigation, Juan Carlos could become a target in two inquiries in Spain and Switzerland.
The 82-year-old former monarch has been living in the United Arab Emirates since he left Spain in August.
On Friday that Juan Carlos had travelled by private plane from Spain to the United Arab Emirates on Monday.
"We have to clean up the system of corruption and we should start with the crown."
Juan Carlos; video about the effects of the virus on tourism; and Aberdeen footballers.
His lawyer, the royal palace and the government have all declined to say where he is.
Letters written from King Juan Carlos to his son and King Felipe’s reply were published by the Palace on Monday
The former king has informed his son that he will live outside Spain.