Crackdown on illegal immigration or are the special interest groups for illegal aliens cracking down on the crackdown?

Some towns are taking it upon themselves to crackdown on illegal immigration. Now the special interest groups for illegal aliens are suing them for doing so -- claiming that the laws are unconstitutional. Basically, the towns were tired of the federal government not doing anything about it and took it upon themselves to inact local laws.

One of the things I found interesting about was the the interest groups claim on one subject from the article:

"Riverside's ordinance is placing business owners and landlords in a predicament whereby they will be afraid to hire or rent to a legal immigrant who is perceived to be an 'illegal alien,' thus giving rise to national origin discrimination," it contends.

I don't see the predicament. So, I did some research. I went online to see what is required fields to fill in on an apartment application. Turns out that there were several not-so-suprising surprises. A social security number is required on every application that I ran across. Same goes for all the job applications I ran across.

Where's the predicament? If I am a renter or business owner and no SSN can be provided...sorry, can't rent it. Can't hire you. Predicament solved right? I am sure there are other gray areas here, but it seems to me that there is a list somewhere to prove citizenship and that should be easy. If the documents are forged...then that's the cops problems.