Employer problems

I have a friend who works at a bar but the employer doesn't let him quit despite the fact that he told him that he wants to quit but got no paper whatsoever

More then that , the employer is threatening him that he cannot leave the job and so forth

Also he didn't get a copy of the labor contract and the promises weren't kept

Would it be alright to sue the employer?

My friend is from Romania

I would DEFINITELY consult a lawyer.

Idk about Romanian law but in the states

most jobs are "at will" and you can leave

any time you like.