Comment by caturopath

Yes, there are unilateral policies and treaties that let the US and the UK collaborate in legal action (going through US institutions to judge them), some of them referenced in https://meta.wikimedia.org/wiki/Legal/Legal_Policies -- a keyword might be letters rogatory

Wikimedia also seems to have a presence in the UK https://wikimedia.org.uk/ that presumably would be affected.

In most cases they might have enough pull to get folks blacklisted by payment processors, but wikimedia in particular might win that one.