Earlier quoted context omitted.
I see that Gitlab does not currently hire in some locations (e.g. France, Italy or Spain). Is it because of local laws or other reasons ?
Local law is the most common reasons although there is also non-local law such as US sanctions and other reasons. For a complete list see https://about.gitlab.com/jobs/faq/#country-hiring-guidelines
A Spanish citizen can work for a company registered in any other EU country without any problems.