I don't think that's true. I do know that they can't ask if they are here legally. In fact, they are required by law to verify the SS#. However, they need go no further. All they are required to do is match the SS# to the name. They are not required to verify if the name and SS# are being used by more than one person.
Bingo. That loophole was created so that Tyson and everybody else could go through the motions of the I-9 process and hire millions of illegals without fear of economic/criminal reprisal. Imagine only having to verify that a SS exists - but not whether it is valid or actually belongs to a little old lady from Pasadena.
This is the type of thing that Bush could have resolved long ago by the simplest of directives either through the Depts of Labor, Agriculture (disease, etc), DHS/ICE, IRS/SS Admin, etc - but he didn't want to.
He didn't want to because illegals are a boon to our nominal accounts (eg unemployment, inflation, etc). That's why he has willfully aided & abetted allowing illegals to thrive in our communities. But he's wrong about the benefits they bring because it back loads their true cost onto the balance sheet ie our government expenditures to support illegals.
And he's especially wrong about their impact on communities. The 'Day Without Illegals' did us all a favor by exposing these folks for what they are - and Bush now needs to do reverse course or face Articles from a Dem House in 2007.