Okkkkkay so I'll play your hypothetical game.

So in your scenario here, some enterprising individuals start off by smuggling alcohol into the UK. By definition according to Merriam-Webster, smuggling is: "to import or export secretly contrary to the law and especially without paying duties imposed by law".

According to UK laws, this has the following consequences:

Penalties for Drug Smuggling
The legal consequences of drug smuggling in the United Kingdom are robust and intricate. These penalties are designed to deter and punish those involved in the illicit trade of controlled substances, and they vary significantly depending on the nature and scale of the offense.

Prison Sentences
Convictions for drug smuggling can result in substantial prison sentences. The duration of imprisonment varies based on factors such as the type and quantity of drugs involved, the defendant’s role in the operation, and any previous criminal history. For Class A drugs like heroin or cocaine, sentences can range from several years to life imprisonment. The courts take a particularly stern stance on those involved in large-scale drug trafficking operations, often imposing the harshest sentences.

Fines
In addition to imprisonment, courts may impose hefty fines on individuals convicted of drug smuggling. These financial penalties are meant to act as both a punishment and a deterrent. Fines can be substantial and are typically proportional to the severity of the offense and the defendant’s financial means.

Confiscation Orders
The UK’s legal system has mechanisms to prevent criminals from profiting from their drug smuggling activities. Courts can issue confiscation orders requiring the defendant to surrender any assets or wealth acquired through drug smuggling. This means that criminals face prison time and fines and risk losing ill-gotten gains.

Forfeiture of Assets
In cases where assets such as vehicles, boats, properties, or other possessions were used to commission drug smuggling offenses, law enforcement agencies can seize these assets through forfeiture proceedings. This serves as a punishment for the offender and a means to disrupt criminal enterprises.

Travel Restrictions
Convictions related to drug smuggling can result in travel restrictions imposed on the individual. These restrictions may include bans on leaving the country to prevent the convicted person from continuing their criminal activities abroad. Such measures are implemented to ensure that those involved in drug smuggling cannot easily evade justice by fleeing the country.

Lets move to the selling of the illegally imported alcohol:

You can be stopped, fined or arrested by police if you’re under 18 and drinking alcohol in public.

If you’re under 18, it’s against the law:

• for someone to sell you alcohol
• to buy or try to buy alcohol
• for an adult to buy or try to buy alcohol for you
• to drink alcohol in licensed premises (such as a pub or restaurant)

However, if you’re 16 or 17 and accompanied by an adult, you can drink (but not buy) beer, wine or cider with a meal.

If you’re 16 or under, you may be able to go to a pub (or premises primarily used to sell alcohol) if you’re accompanied by an adult. However, this isn’t always the case. It can also depend on the specific conditions for that premises.

It’s illegal to give alcohol to children under 5.

For the sake of your argument, we'll remove the law that says its illegal to sell alcohol to children, I guess? Regardless, it might be some enterprising individuals that are selling it, but they are selling the alcohol in the UK. In UK currency, To UK residents. In the UK. We are getting into possibly exchanging UK currency for US currency, which is a whole new can of worms, but we can save that for later.

Now to your question:

now, do you still think the UK government has a right to fine 4chan or do you think maybe the UK government should elaborate on their prohibition regulations to ensure their citizens are properly “protected”?

Easy answer is yes. They should be fined for smuggling alcohol into the UK, which is what the current law calls for.

Now hypothetical for you.

Imagine for a moment that the UK has banned looking at alcohol if you are under 18. Doesn't matter if you look at alcohol if you are over the age of 18, but you just can't legally look at alcohol if you are under 18.

Now someone comes along named 4chan and builds a giant building in the UK that has a ton of alcohol inside of it. There isn't anything outside of the building. Its only inside where the alcohol is. They don't have protections in place that prevent anyone under 18 from going inside the building. Anyone can come in and look. You can be 5 years old, or 100 years old. As a matter of fact, tons of people from all over the UK come and visit this building daily, even children.

Now the UK government comes along and says, "Hey 4chan, you need to verify that anyone that goes into your building is at least 18 years old, because if someone under 18 looks at the alcohol in there, thats against the law."

4chan ignores the UK and continues letting anyone inside, not verifying anyone's age. Not only that, but they're actually selling alcohol to children in there, and letting children make their own alcohol as well.

Should the UK be allowed to fine/arrest 4chan until they meet the demands?

Then explain why you disagree instead of coming at them with ad-hominem.

I didn't delete it lol. And its happened just as I said.

Because they're doing business in that region. You don't just get to go to another country and do business as you please there.