If you don't oblige the requirements of your contract, whether in the USA or Europe, your employer has a legal right to sue you for consequent damages of your immediate resignation.
Not likely to get sued realistically, though. The real penalty is that the employer could give you a poor reference, which absolutely will lose you jobs.
I think in europe you generally need to give notice. The length of that resignation period varies between countries and work contracts.
How can they enforce it though? Like if you just don't show up, they can't force you to work
If you don't oblige the requirements of your contract, whether in the USA or Europe, your employer has a legal right to sue you for consequent damages of your immediate resignation.
Not likely to get sued realistically, though. The real penalty is that the employer could give you a poor reference, which absolutely will lose you jobs.
The employment of many (most?) European professionals is governed by a contract, so there are probably terms about what kind of penalties may apply.