German campaigners have lit celebratory joints after the country liberalised rules on cannabis to allow possession of small amounts.

The German Cannabis Association, which campaigned for the new law, staged a “smoke-in” at Berlin’s landmark Brandenburg Gate when the law took effect at midnight.

Other public consumption events were scheduled throughout the country, including one in front of Cologne cathedral and others in Hamburg, Regensburg and Dortmund.

The new law legalises possession by adults of up to 25 grams of marijuana for recreational purposes and allows individuals to grow up to three plants. That part of the legislation took effect on Monday.

German residents aged 18 and older will be allowed to join non-profit “cannabis clubs” with a maximum of 500 members each starting on July 1.

Individuals will be allowed to buy up to 25g per day, or a maximum 50g per month — a figure limited to 30g for people under 21. Membership of multiple clubs will not be allowed.

The clubs’ costs will be covered by membership fees, which are to be staggered according to how much marijuana members use.

The legislation also introduces an amnesty under which sentences for cannabis-related offences that will no longer be illegal are to be reviewed and in many cases reversed.

Regional authorities have voiced concerns that the judicial system will be overwhelmed by thousands of cases.

The law was pushed through by the coalition of Chancellor Olaf Scholz’s Social Democrats, the Greens and the pro-business Free Democrats, against opposition from some of Germany’s federal states and the centre-right Christian Democrats.

Christian Democratic leader Friedrich Merz has vowed that his party will reverse the legislation if it wins national elections expected in the autumn of 2025.

Leading garden stores surveyed by the dpa news agency indicated they would not be adding cannabis plants to their horticultural offerings, and the German Medical Association opposed the law, saying it could have “grave consequences” for the “developmental and life prospects of young people in our country”.