French work permit/visa Transfer

Does anyone have any information about transferring a visa/work permit from one company to another?

Is this possible under french law? Or are the work permits associated with particular companies?

I have a potential employee who has gotten the confirmation from the french government confirming his work permit in france. He would now like leave that company and work for another.

Does the second company have to reapply for the visa/work permit?

Any help would be appreciated