I manage a community garden in Montreal and love the idea of BBQ and beers in the evening, but the city, (who owns the land), is not ok with drinking at the garden, (or cooking, in general).
If you want a translation (to convince Montreal to adopt similar laws?) you'll need to find someone to translate it for you.
If that page is the whole set of laws then it's really not so many rules as the article makes out - our rules in Montreal are probably just as long. I'm going to see if I can cherry-pick the best parts for my little corner of Montreal.
I Google Translated the federal law, and it seems to be mostly about how leases are dealt with. I also did some Googling and found what I think is the garden in the article, although there seems to be a few gardens in Wedding. They're big compared to what we have here in Montreal.
I doubt you find much about alcohol consumption in this law since in Germany you are allowed to drink in public at 16 years old (14 with your parents)