There have to be limits to the employer/employee contract. Since most employees in the US work At Will, without any contract, then the government has to have some basic intervention in the system. The difficult part is to figure out where the line between not enough and too much intervention is.
Without government regulation, employers would be back to where we were in the late 1800's. Read "The Junge" by Upton Sinclair. This is what happens when the free market system is allowed to operate with minimal or (too) limited regulation.
The free market cannot provide fairness for everyone. A fully free market would have employees as slaves, serfs and indentured servitude.