Federal law but there are some restrictions.
They do not have to pay you for the time off.
You have to have been employed and worked a certain number of man hours.
Your best resource is your Human Resources rep (office)
There is paper work that has to be filled out. You can't just say well, I am being induced tomorrow, I will see you in 6 weeks.
It doesn't work that way.
Why would Illinois be any different than anywhere else?