I'm on the fence in regards to this issue. While I see nothing wrong with allowing workers the choice of working 7 days a week, I agree with Kondor that something is fishy.
Also it's naive to believe that companies won't require you to work for 7 days straight. I have worked for companies that have done it in the past. If you didn't like it they would fire you and replace you in a matter of hours. Many people out there are looking for work, and will do as they are told to keep their job.
WHY is government involved is more the issue.
Why are there child labor laws?
Indeed, why are there labor laws at all?
Because, of course, in the past, there was widespread and large-scale abuse of workers by business, and organized labor stepped-in and leaned on legislatures until laws were crafted and enforced that offered some relief against those abuses.
That was then, and this is now.
We have lived 2-3 generations now without the worst of the rampant abuses that organized labor was created to fight against.
But that potential still exists, lurking just below the visible surface of present-day business/labor relations.
We have grown too trusting of business to behave itself.
Remove the protection of such labor laws (or, at least, their updated modern successors) and you set the stage for a return to the very abuses that labor fought so hard to halt, in the time of our grandfathers or great-grandfathers.
And, given that Republicans have become associated with a role as mouthpieces and front-men for Big Business in recent decades - having long-since lost its grand old position as the party of the common man - nobody trusts such an initiative when it comes from a Republican.