I think the title of this article is a bit misleading – it’s not about the legal status of employment, but about the legal status of your work. Many people who are in a position to work legally for someone else are actually not authorized to work for them because they don’t have the necessary permission.
That’s not to say they don’t work for other people. They work for all parties, sometimes even with legal permission. We can’t get permission to work for anyone else.
While they are not authorized to work for anyone else, they can legally do various things for other people. They can work for the person who hired them, they can work for their employer, and they can also work for the company that hired them. While they are not legally authorized to work for anyone else, it is a legal requirement to have permission to work for someone else.
While legal, we are unable to work for anyone else. This is the point of being legally authorized to work for someone else.