The partial legalization of cannabis for personal use, which was championed by the centre-left government of Chancellor Olaf Scholz, takes effect in Germany on Monday.
The Bundesrat or upper house let the long-debated bill pass last month after it was approved by the lower house, the Bundestag.
The landmark legislation allows for adult possession of up to 25 grams of cannabis for personal use in public.
Three live cannabis plants will be legal in one's own home and up to 50 grams of cannabis for personal use there.
Smoking weed in public spaces is to be banned in schools, sports facilities and within 100 metres of these facilities.
The SPD, Greens and liberal FDP launched the plans despite great resistance from the opposition, the federal states and also from organizations.
The government argues that the prohibition policy has failed and that cannabis consumption has increased despite the ban.
The aim of the law is to combat the black market and reduce health risks. The active ingredient content of cannabis purchased from dealers is unknown and toxic additives and impurities could be present.
The conservative opposition Christian Democrats (CDU/CSU have vowed to revoke the legislation if they gain power:
"In our view, drugs policy, particularly with respect to protecting young people, is an issue of such central significance that we will revoke the legalization of cannabis in the event we take power," lawmaker Thorsten Frei told the Augsburger Allgemeine newspaper in remarks published on Saturday.
