Who is affected by SB 1070?

The law reads:
"The provisions of this act are intended to work together to discourage and deter the unlawful entry and presence of aliens and economic activity by persons unlawfully present in the United States."
http://www.azleg.gov/legtext/49leg/2r/bills/sb1070s.pdf

Really!? Aliens! Well, golly. I guess they do exist.

But seriously, let's keep reading and see if we can understand what they are saying here...
"WHERE REASONABLE SUSPICION EXISTS THAT THE PERSON IS AN ALIEN WHO IS UNLAWFULLY PRESENT IN THE UNITED STATES, A REASONABLE ATTEMPT SHALL BE MADE, WHEN PRACTICABLE, TO DETERMINE THE IMMIGRATION STATUS OF THE PERSON." (This was in caps in the document. No, I'm not yelling at you.)

Okay, so let's do a close reading on this.
1) We are looking for people who are "aliens"
2) If there is "reasonable" suspicion, then we pull them over, stop them on the street, etc. and check their identification.

So, now we're getting somewhere. If we see people who look like aliens, we stop them because they must be "illegal" and even if they're "legal" we need to check because we're all safer that way.

But I still don't know how you tell someone is an alien? Because if we don't have a definitive idea of who is and who is not an alien, isn't there potential for pulling over or stopping EVERY single person in the state of Arizona? Surely the police people have better things to do, like enforcing laws that actually protect people instead of harming them.

For my next post...
What is an "alien"? Am I an "alien"?