This is complex. Firing can often be legally challenged and reinstatements demanded. Making any law that is only tenuously constitutional, probably only under the totally violated commerce clause, then it produces more legal mischief that only lawyers would gleefully welcome, but not taxpayers or employers or even employees. Now, when it involves labor unions isn't there already all manner of public discussion of employee wages, as their primary concern? So saying yea or nay here is irrelevant.