It's important to note the feds do all sorts of things not spelled out for them in the constitution, and often that actively contradict the constitution. In fact the feds already have a law interfering with time off, the family and medical leave act of 1993.
Granted, that law only allows unpaid time off where employers have to take the employee back, and it only applies in certain circumstances. But my point is they would step over the constitution in a heartbeat, as they have done countless times, if they wanted to.
The important detail is that the United States gives the power to the states, who make the laws.
You accepted (and utilized with references) the crux of my argument in order to debunk the strawman offered alongside.
Granted, that law only allows unpaid time off where employers have to take the employee back, and it only applies in certain circumstances. But my point is they would step over the constitution in a heartbeat, as they have done countless times, if they wanted to.