If 4chan continues to ignore Ofcom, the forum could be blocked in the UK. And 4chan could face even bigger fines totaling about $23 million or 10 percent of 4chan’s worldwide turnover, whichever is higher. 4chan also faces potential arrest and/or “imprisonment for a term of up to two years,” the lawsuit said.
Not just “sometimes”. The thing you’re looking for is “jurisdiction”. A country doesn’t have jurisdiction in another.
The comment I replied to talked about trying to fine websites based outside the respective country. Countries obviously still try that