Royal Decree-Law 9/2022, of March 27, which included labor measures to mitigate the effects of COVID in the labor market, established that terminations for objective reasons related to the Coronavirus would be deemed "unjustified”:

“Force majeure and economic, technical, organizational, and production-related causes underpinning the suspension of contracts and reduction of working hours as provided in Articles 22 and 23 of Royal Decree-Law 8/2020, of March 17, shall not be considered valid grounds for terminating employment contracts or for dismissal.”

The fact that a dismissal is considered “unjustified” leads to a declaration of unfair dismissal, not its nullity.

This was the interpretation we, as legal professionals and scholars, upheld from the outset, in contrast to the position repeatedly expressed by the Government and the Ministry of Labor in the press during the most difficult and critical phase of the pandemic.

I don't know whether this was left ambiguous by mistake or on purpose. The reality is that the Government's failure to clarify this issue created legal uncertainty and a great deal of litigation (which meant more lawsuits and further overload of the judicial system).

Years later, the Supreme Court has finally clarified the matter.