Specifically which parts of Europe? It's a big place, and I have given negative references with no fear of liability. And that includes across EU borders, including the UK.
On the flip side, a reference has an implicit duty of skill and care to both the former employee and the person asking for the reference, so an overly-positive reference can also lead to legal liability from the person asking for the reference.
In some regulated industries the content and form of references is also regulated as well, for example see pages 11 and 31 of https://www.handbook.fca.org.uk/handbook/SYSC/22.pdf
(None of this is legal advice)