(Bloomberg) -- An association representing Germany’s new cannabis clubs has warned regional lawmakers that they risk scuppering a controversial law legalizing personal use of the drug if they don’t approve it in the upper house of parliament next Friday.

The legislation introduced by Chancellor Olaf Scholz’s government was signed off in the lower house of parliament last month and is meant to take effect April 1.

However, lawmakers in the Bundesrat upper house, where Germany’s 16 states are represented — including some members of the three parties in Scholz’s ruling alliance — have expressed reservations about the law, a first step toward a planned broader legalization. While it doesn’t need their formal approval, they can delay its passage and send it to mediation for potential changes.

Under the new rules, adults would be permitted to possess a maximum of 25 grams (0.88 ounces) of cannabis for use in public and grow as many as three plants for private consumption.

From July 1, cultivation in nonprofit cannabis clubs limited to 500 members would also be allowed. They are meant to ensure the broad availability of high-quality cannabis at competitive prices in order to channel demand away from illegal dealers.

CSC Maps, a group representing around 300 of the clubs, published a letter Friday that it said it has sent to regional lawmakers urging them to approve the law.

Otherwise, the partial legalization on April 1 “will inevitably be off the table,” they warned., adding that “there is a threat of months of delay and even the end of the law.”

Germany is following countries including Canada, Uruguay and Malta, as well as around 20 US states, which have introduced similar mechanisms for the controlled use of cannabis.

Health Minister Karl Lauterbach has said the government is pursuing two main goals: to tackle the illegal sale of the drug and to better protect the health of young people.

CSC Maps was launched last year by Berlin-based Greenrise GmbH, part of a group of companies investing in the cannabis market.

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