Ok, hypothetically though, and going back to the smoking in Paris law, if the UK banned smoking in Paris, and a French citizen proven to have smoked in Paris vacations in the UK, the only thing stopping the UK from prosecuting them is that it would be kinda "act-of-war-ish" to start imprisoning French citizens. Technically they could under their own law, they just wouldn't dare since they don't want to start a major diplomatic incident or war.

Once you're in another country's jurisdiction, all bets are off. You're subject to those laws, unless there's a treaty or similar saying that you're not. In another post, I mentioned writing nasty blog posts about Kim Jong-un. If you do that, it's probably a very bad idea to visit North Korea.

In this case, the operator of 4Chan is free to blow off the UK's law. They may wish to account for that in future travel plans, though.

This is why we are not travailing the US right now.

Because you think ICE will arrest you for being an illegal immigrant? If you seriously believe this, then probably its best you don't go outside anymore.

Every time the media reported something like this, turned out they were leaving out something important. Like the professor who was smuggling biological samples into the US. Turns out that's illegal, that's why she went home. If you aren't doing something like that, you will be fine.

As someone who has travelled a fair bit across the border between Canada and US, CBP agents have always tended to be dicks drunk on their power. I've seen plenty of blatant abuse at the border. So really the only thing that needs to happen for CBP to ruin your day is for an agent to have a bad day for their own. The only difference between then and now is that they're given more tools to do so and actively encouraged to use them.

Yeah these people that think there is any measurable risk to going to the US as a normal tourist or businessman respecting US laws while there really need to get out of whatever bubble is feeding them that fear.

This is also why a lot of people refuse to travel to the UK now.

That's reasonable.

This is one of those technically true but defacto false things. Its legal under UK law, but if they want the variety of benefits they get from the US then it isn't. If the UK government starts arresting vacationing Americans for things that aren't a violation of US law, its all a matter of if the US governments wants to make an issue of it. Maybe you get lucky and nothing happens, or maybe you lose your military protection and 25% of your GDP. Plus your tourism businesses take a hit. You really want to take that risk?

But given the behavior of the UK government lately, doing something suicidally stupid seems on brand for them.

The US have done this a lot, luring “hackers” and other criminals to the US and then arresting them.

I declare categorically that UK law does not apply to me, here in California.

However, if I'm going to break one of their laws that they feel very strongly about, I'm probably not going to travel to the UK. That's just begging for something bad to happen. Why risk it?

So in this case, if you know the US is looking for you, why, oh why, would you travel to the US?

They can issue an arrest warrant, though, and then file an extradition request to the US which you then have to fight.

The US doesn't extradite citizens for things that are not a crime in the US.

That's the "you then have to fight" bit.

There are a few cases of claiming universal jurisdiction criminalizing what citizens of other countries do even outside the country, but that's generally things like crimes against humanity.

Boats are considered the territory of the flag state.

> America will not arrest or prosecute someone from the UK visiting Thailand as a sex tourist.

Sure it will. Citizenship is irrelevant. If you travel abroad to have sex with underage people and then come to the US, you can be prosecuted regardless of your nationality.