(To me, the salient section is: "Spain's 1978 constitution makes an assault on the monarchy virtually impossible. In order to hold a referendum on the monarchy, two-thirds of members of the Spanish Congress and Senate would have to vote in favor of the proposal, and immediately afterward the parliament would have to be dissolved. Two-thirds of the successor Congress and Senate would have to ratify the same motion, and only then would it go before the Spanish public which would have to vote in its favor to make it successful.)...
... for which, however, the article is critical.
https://www.politico.eu/article/spain-republicans-juan-carlos-exile/
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