In the spirit of the law/regulation that's even worse: as an immigrant without permit to do that, he'd provide unpaid labor undermining ability of other people

In the spirit of the law/regulation that's even worse: as an immigrant without permit to do that, he'd provide unpaid labor undermining ability of other people compete for this job. Edit: of course IANAL. And in other words, as I understand it, work permits limit strictly to what extent can you affect competition in the country (H1b - only one FT job position). And by filling in vacuum of required labour somewhere else you definitely affect it negatively.