In Marbella there are more than 20,000 illegal properties that have been built on United Nations protected habitat

Properties constructed without a building licence issued by the respective Town Halls will always be illegal until they have been legalised, if it is possible, under the existing laws.

Properties built with a building licence issued by the Town Hall should be legal.
Surely this is why purchasers use the professional services of lawyers and Notarios to ensure that there are no illegalities with their properties when they buy.

Retrospectively cancelling building licences, as is happening now, will not encourage people to buy in Spain.

The biggest loser in the long run will be Spain.
One million expats spending on average 1,000 euros a month will not be easy to replace in the economy of Spain.

Good point, Dennis. That’s a lot of money. And the whole planning and building licence issue is a total fiasco.
Fortunately, however, in some areas the locals have realised how much the investment by northern Europeans in the local economy (property purchase, car, shopping, employment, tax, etc) has improved their lot overall. And as a result relations between locals and immigrants are very good. Many small villages that were crumbling rural backwaters 20 years ago are now spruced up and thriving.
By the way, just signing on the padron brings 2000 euros a head per year to your local council (so why not do it today – it takes about 10 minutes, if that, and costs nothing!)