This is another difference from the US. Certain forms of solidarity action are illegal in the US.

The TL;DR of US labor law is:

1. Companies do [very illegal under local law, up to and including murder] things to bust unions; they buy off the local authorities to get away with this.

2. The Federal government adds specific protections for unions -- many of which don't exist in various European countries.

3. Companies complain that #2 makes unions too powerful, so the Federal government adds specific restrictions on unions -- many of which don't exist in various European countries.

I'm curious about the history in Europe, since an equilibrium seems to have been found without steps #2 and #3.