The Constitutional Court has held unconstitutional a provision in a law passed by the Catalan parliament which, if a loan secured with a home is sold to a third party (a fund usually), allowed the debtor to be released from their debt by paying the buyer out of the debt only the price the buyer had paid (plus the statutory interest and costs caused by the claim).
Although this new route for discharging mortgage debts never came into operation because the Constitutional Court stopped it provisionally while the appeal was being studied, if it had been held valid, its effect would have been that no entity (including a securitization vehicle) that had acquired a loan, credit facility, or mortgage-backed security would have been able to claim from the debtor an amount higher than the price paid by that entity to the bank that sold the debt (except for statutory interest and claim costs).
The Constitutional Court held that a provision of this type encroaches on central government powers because it lays down a new substantive rule, relating to the specific amount that a debtor must pay to be released from the mortgage on their home. The Plenary Session reminded us that, in matters of government powers, the basic rule is that autonomous community legislation cannot introduce rights or obligations in the context of contractual relationships between parties because private law is reserved to the power of central government.
In the same decision, the Constitutional Court concluded that the guarantor of a mortgage requested to buy a home cannot automatically benefit from discharge of the liability covenanted between financial institution and debtor, not even if there is a family relationship between guarantor and debtor. That option to release the guarantor automatically from their obligation has therefore been held unconstitutional, whether within an out-of-court voluntary mediation procedure or within a court proceeding (a proceeding also held unconstitutional and null and void in the same judgment).