This explanation helps me understand Michigan, but
here in Texas (a "right-to-work" state already, and very few Unions exist here), what it means is giving up your rights as a worker. You must sign an agreement when you are being hired which states that you can be fired at any time without reason.
Isn't that great?
I screwed up one recent job interview by mentioning how ridiculous I think that law is, as I was signing the agreement on my application. The Employer looked at me and said, "but it's the LAW!"
I told him that understood that it is the law, but that I thought it was foolish to sign away all of your rights like that. I signed anyway, because you have to (to even be considered). The rest of the interview process had gone great, and I was qualified for the position, but I never got a call back.