Telemedicus has an entry on Wikipedia in deutschen Gerichtsurteilen. It refers to the German Wikipedia article on the subject. It says that the Bundesverfassungsgericht doesn’t cite Wikipedia, but it does cite weblogs (link to LAWgical), on the topic of dual nationality for Turks.

Here is the Unabhängiger Verwaltungssenat des Landes Oberösterreich:

Der offene Boden zwischen Gemüsepflanzen, Blumen, Sträuchern und Bäumen wird hierbei mit organischem Material wie etwa Rasenschnitt, Beinwellblättern oder anderen Gartenabfällen bedeckt (vgl. www.wikipedia.org).

There is an English Wikipedia article on the same subject, and a link from there leads to an article on when it is appropriate to quote Wikipedia, plus footnotes discussing various citations.

For the UK, I did a search of BAILII and found only 11 hits. Some were for the European Court of Human Rights, and the others were cases where one of the parties cited Wikipedia.

The ECHR does cite Wikipedia on the ethnic composition of Latvia.