Hi Claire, nice to hear from you, I have been away from the forum for a while for few reasons.
Only exceptionally an spanish law would be retrospective.
The andalusian law I mean was a subject in one of my postings, I made a long translation into english of it contents ( I am sure you can find it, something like new law protecting consumers ). It mainly tightens the control on sale of off plan properties and obviously one of te main requirements is the Bank Guarantee. This new regulation is rather new and it implements the DIA (Documento Informativo Abreviado) which ALL developers AND agents selling off plan properties MUST have in their sales offices. The information that DIA must contains is rather long to repeat it here, please read my posting regarding that subject.
But the legal duty for the developers to issue a bank guarantee to buyers comes from an old law, as old as 1968!, after that year there another laws enforcing and confirming that legal obligation for the developers.
Honestly Claire I cant imagine many buildings in the Costa del Sol older than that.
José María Sánchez Alfonso
Costa del Sol, Málaga