Give a 6 months notice that the law will go into effect and anyone caught without a valid workers permit will not only be deported, but they will never be allowed back in the country. That way you don't have the expense of rounding them up and deporting them. If they have a current job, their employers can attest that they have a job waiting and they should be immediately issued permits FROM THEIR OWN COUNTRY AND ONLY IF THEY ARE THERE IN PERSON!
"Give a 6 months notice that the law will go into effect and anyone caught without a valid workers permit will not only be deported, but they will never be allowed back in the country."
They wouldn't move. They know the ACLU and other legal fascists would be to their rescue and a knucklehead lib judge would stop the thing.