Arizona is legally entitled. per the Supreme Court, to determine the immigration status of anyone that is involved with any routine altercation with the law. The the Department of Homeland Security issued a memo telling agents not to take action regarding anyone that the state has in custody unless the people are criminals.
A criminal is someone who has violated a law. One of the laws of the United States is that you are not allowed to enter the country without the government allowing you to be here. You must be here for a specific allowed purpose, business, tourism, politics, or to immigrate, meeting the limits and restrictions on that latter category that the government has placed. The Congress has set caps on who is allowed to come and the limit per year from each country as well as restrictions on people who might be a threat to this country. Entering other than this way violates US law. By definition, someone who does that is a criminal.
Now, given the lack of any ID or registration or means of identifying illegal aliens, unless they are cought in the actual commision of a crime OTHER than being here illegally, they Department of Homeland (in)Security has defined them as automatically NOT illegal.
Now the executive branch of federal government is making its own laws, negating the laws passed by Congress, by not doing its duty. As the executive branch, their duty is to perform the laws passed by our Congress. Instead they are executing the law, by killing it.
So why is it that citizen still have to pass through customs and immigration when returning from a trip? Why do we have to be groped at the airport when there would be no such bother if we had walked into Arizona from Mexico?