What law regulates public procurement in Spain?
Well, here is the explanation without so much academic roll:
In Spain, the Public Procurement Roll is sent by Law 9/2017, the famous Public Sector Contract Law (or LCSP, if you want to sound pro). This law basically adapts what the European Union on public contracts says, so it is not just our invention. If you ever have to deal with paperwork to sell something to the government, this is the law that will persecute you.
The LCSP puts the rules of the game: how suppliers are chosen, what kind of contracts there is, and how everything should be clean, without favoritism or friends (at least in theory). It seeks that everyone who wants to present themselves to a tender have the same opportunities and that there are no scams.
Who does it affect? Well, almost everyone in the public sector: from the central government to the town halls, going through social security and other organizations that sound boring but that handle a lot of pasta.
There are several types of contracts under this law: works (plan and build things), supplies (sell things to the State), services (from cleaning offices to consulting), and also concessions, which is when they let you exploit a public service for years. Each type of contract has its own rules, but everyone has to follow the basic principles set by law.
And how are these contracts awarded? Well, there are several paths: the open procedure (everyone can appear), the restricted (only invite you if you are VIP), the negotiated (they speak with you directly, with or without prior ad), the competitive dialogue (brainstorming roll between company and administration) and even one to innovate, because the law also wants new things.
A notice for companies: if you don't know this law, you can paste it. Here the "I did not know", because if you, you stay out of tenders or you fall a sanction. So the typical thing is to have someone who knows the subject or, minimum, be attentive to the changes, because the law lives in constant update (yes, more paperwork ...).
In summary, the Public Sector Contract Law is the rule to sell anything to the Spanish State. If you want to play in that field, you have to study it yes or yes, or better, have someone to dominate it. Because, believe me, here ignorance comes out.