> Berlin politics

Berlin citizens. It's a public referendum.

> seizing landlords' properties

with 3000 or more units.

> defending against an illegal law

It's not a law and it will very likely never be one as it's pretty much against the constitution.

It's not illegal. It's in the German constitution. Land is seized all the time, too. E. g. when the autobahn or mining operations are expanded. Nobody bats an eye there. It's only when corporations shift from being beneficiaries of disappropriation to being the target of such laws that the whole world all of a sudden is outraged.