IANAL, but I assume this could open Wikimedia leadership to charges of contempt and eventually lead to needing to avoid visiting the UK or other extraditing countries and potentially pave the way for asset seizures. You generally don't want to antagonize world power governments.

That doesn’t make any sense. It’s not wikimedia’s responsibility to ensure people from the UK don’t hit their servers by typing wikipedia.org into the browser bar.

That does make sense, but then that would mean that any business not doing business in UK would not have to follow the rule, which would make the rule worthless. But I hope I am wrong.

According to UK law, it is.

Can you cite said law for us?

It's the Online Safety Act. As the government says about the OSA:

"Ofcom is the independent regulator for Online Safety. [...] Ofcom has strong enforcement powers"

https://www.gov.uk/government/collections/online-safety-act

Okay, so what does Ofcom say?

"It doesn’t matter where you or your business is based. The new rules will apply to you (or your business) if the service you provide has a significant number of users in the UK, or if the UK is a target market."

https://www.ofcom.org.uk/online-safety/illegal-and-harmful-c...

I’m sure that they can write that. But their actual enforcement mechanism is nonexistent. No country is going to work with the UK to arrest someone that does that when the same thing isn’t illegal under their own law.

The UK isn't a world power.

Jimmy Wales lives in London.

They have nuclear weapons, are in the G7, are a permanent member of the UN Security Council, 6th highest GDP in the world. What are your criteria?

Having a significant influence over global events.

If Wikimedia blocks access from UK it has control over response page and can write there accurate description of the reasons why access is blocked.