That's more often than not the point - they get to pick and choose where to enforce, likely based on whether or not said user is in competition with them.

Detect might be hard, but enforcing isn't neccesarily so. You file a civil lawsuit and then it's up to courts to enforce the contract (as this would be viewd in EU or copyright infringement (in the US).

That's where you've misunderstood Baidu's intent.

They don't care to enforce it, only to check the box that says they told you open weight models are all but illegal in EU, UK, and South Korea.

"You cannot use our models in these regions."

<wink wink> <nudge nudge>

Now it's on the EU, UK and South Korea to stop users from downloading and running those models.

All that said, the EU, UK and South Korea, if they want to, are all more than capable of making life a living perdition for people who do run those models. So I wouldn't say it's "not enforceable". Only that it probably won't be enforced in the fashion one would think these rules would be enforced.