They can't really enforce the laws that are on the books now because they haven't been enforced for decades. That will blow right through the courts and we all know it. By passing a new law everyone in the country will know that these are the new rules. Those who ignore the new rules will find themselves bankrupt and in jail. There will no longer be the excuse "everybody has done this for decades".
And yes, I think they mean it. This will be very easy to set up tracers on. They already have a reporting program for all new hires (to catch deadbeat fathers) and that can easily be used to cross check the guest worker database.
He also said that workers who violate the law will be returned to their home country and will never be permitted to re-enter.