Here’s the introduction to their  piece

I spoke to Amber Marks, a barrister and criminal law expert at Queen Mary University London, who has published a paper on the legal minutiae around Spanish cannabis clubs, to find out more about how this came about and what it means for cannabis users in Catalonia and beyond.

PAPER

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INTERVIEW INTRO

VICE: Hi Amber, can you tell me why this law was needed in Catalonia?
Amber Marks:

Up until now cannabis clubs in Catalonia have been operating in a grey area of law, because the Spanish supreme court has repeatedly refused to clarify the dividing line between social supply and criminal supply in the context of cannabis social clubs. It has repeatedly said that this is a task for the legislature and that the court will decide guilt on a case-by-case basis. The minority judgments in these cases all pointed out that this was unsatisfactory on account of the uncertainty created. The legislature of Catalonia has taken action by stipulating the parameters for lawful social supply in the context of cannabis social clubs.

What exactly does the new law say?
It provides a statutory regulation for the operation of cannabis social clubs, which are basically private members clubs that supply cannabis cultivated on behalf of their members. The law acknowledges the right of citizens to consume cannabis and the right of cannabis users to get information on the quality and strength of the cannabis consumed.

More at   https://www.vice.com/en_uk/article/qvpknx/we-asked-an-expert-about-catalonias-ground-breaking-new-weed-law

Amber Marks

Biography     Wikipedia