Then they are in their same boat as today; ineligible for government benefits, amnesty, blue cards, green cards, social security, as well as representing increased penalties to any employer who would hire them over one of their fellow illegals who did register.
It is a carrot and stick approach. Both punishment and rewards are being offered to compel registration.
You would see a similar approach if our government was ever taken over by tyrants who wanted to outlaw firearms. They would offer carrots and threaten us with sticks to first get us to register.
The registration is the key to the government's power. In this case, over illegal immigrants. Their advocates, such as la raza, will be fighting President Bush's plan tooth and nail because they know that Registration leads to Confiscation...to put an anti-gun control message to work in this immigration case.