An illegal person shouldn't have a drivers liscense... except maybe from California.

It is funny how many people call on the Constitution to actually defend the Arizona Law.  The law is unconstitutional as in it is in violation of what the Constitution states.  Article 1 of the constitution grants Congress with exclusive powers over Immigration in various forms. Then it also grants implied powers throught the Necessary and Proper Clause.  And then the Constitution expresly provides with a Supremacy Clause.

So, no matter what good intentions or reasons Arizona may have, it is still agaisnt the Constitution of the United States to make such a law.

I read some arguments here that in "other countries you have to..." but you need to keed in mind that the US is not your typical Republic where there is a single government.  No, the US is a federation, so there are many governments working together.  So while Federal law says that if you are an alien you have to carry your passport or permit at all times, a state police officer has no right to demand it; only a federal officer can.  Sounds dumb, but that is just the nature of having two separate governments.  Just like state governments don't like the federal one to interfere in its affairs, so does the federal government.  The constitution gives it some powers and it is not going to allow the States to usurp it.

The whole argument about "well the Feds are not doing it so we have to..." is also invalid.  The reason we have elections is to have the power as a people to vote for officials that represent the views and opinions of the people.  So if you believe your opinion is in the mayority then the elective body should represent that opinion; but if it is not the mayority then you lost.  So the solution to that argument is to vote out the persons currently in power and vote in person who will actually do something about the problem.

So you want a police officer to say the following.

"Excuse me, sir, you were going 5 miles an hour over the speed limit. Can I see your green card please?"

Also, why the hell would anyone from Canada or Britain go to Arizona of all places? Both are among the wealthiest countries per capita in the world. Hell, Canada has a higher development index than the United States, and Britain is 0.009 points lower.

The requirements for a license are more specific than "show one, and you're off." They will only accept licenses from states that require a check before issuing one. (Obviously, AZ is one of them, so they will accept their own licenses.) A license from another country does not prove eligibility to be here, and thus, would not be accepted for this. It would let you avoid driving without a license, though...

@badgenome

Sorry to burst your bubble but the Supremacy Clause argument for this law is not in the context of conflict, it is rather in the issue of preemption (and the injuction to the law was made on this point).  Especifically, implied preemption, which states that where Congress has a occupied the subject area to the preclusion of state laws because of the nature of the federal interest or the pervasiveness of the federal regulatory scheme.

Now, if you want to debate this issues with me you are welcome to do it.  Although I will disclose to you that I am an immigration attorney practicing in California.

Congress can't really be said to occupy the field in this case for a number of reasons, and especially not when the feds rely so heavily on states to help them enforce immigration law. And again, the Supreme Court has upheld the right of states to make laws in regard to immigration status, as in De Canas v. Bica.

i understand, but what im really after is...if the police suspect someone of being an illegal immigrant...how could they determine wether they are really an illegal or just visiting. 

De Canas v. Bica, decide in 1976, decided that a specific California statute was not in conflict with the federal law and the law was not traditionally occupied by the feds.  In that case, the CA law prohibited employers from knowingly employing persons not authorized to work.  Back then there was no Federal statute regarding such penalties, as the employer sanctions law was not acted until 1986.  Now De Canas did lay out a 3 prong-test to check whether or not a state law is preempted.  the Arizona Law does not pass the test, espcifically the second prong of the test.

Now whether the feds are being efficient at their job is another argument. But is irrelevant to the legal issue.  And the feds reliance on the states in this case it is actually because the federal government partnered with state agencies as it is within the feds power to do so.  Congress can grant the state police the power to check immigration status if it wants to.  But the state cannot do it on its own.