How can Someone from Europe work legally in the US?

There is a current court case that is going on right now that specifically affects H-2B visas. You should advise your friend to consult with an immigration attorney (many offer free consultations) about his other options (depending on his education, work experience, etc.) Good luck!

The first step is that your friend needs to find an employer that is willing to sponsor him. He should consult with an immigration attorney to thoroughly review his background and qualifications to determine what visa options are available to him once he finds an employer willing to sponsor him.

If he does not have a four year degree from a university, then his best bet may be file for a student finish, finish his degree and get time to work here on OPT (optional practical training). However, there were not enough details to make a full assessment of your friend's case so my advice is to go speak to someone in your area about other possible options. Good luck