There is basically no difference between a new Arizona law and federal law, says Chris Van Wagenen, a supervisory agent of the U.S. Border Patrol in Yuma, Ariz.

The Arizona law requires police to do what federal law already requires Border Patrol agents to do, he said.

Both require a reasonable attempt be made to determine immigration status of a person during any legitimate contact if reasonable suspicion exists that a person is an illegal alien, Van Wagenen said.

Border Patrol agents or police can initiate conversations with people, whether they are hiking in the desert or on a city street, and if they find reasonable suspicion that a person is an illegal alien, they are to pursue it, he said.

An apparent difference is the stopping of vehicles.

Van Wagenen said police can't pull vehicles over solely on suspicion of immigration violation. They have to have some other cause like speeding or running a red light.

Border Patrol agents may pull over vehicles on articulated reasonable suspicion of an immigration violation.

"It's not just race or fear. It has to be circumstances like a vehicle riding low, with dirt on its tires (indicating its been off road) and in an area known" for illegal immigration, he said.

Reasonable suspicion is a lesser threshold than probable cause, which is the almost certainty that a crime has been committed, he said. Probable cause is needed to make an arrest or to stop a vehicle for something other than an immigration violation, he said.

Lack of ability to speak English is an articulated fact sufficient for reasonable suspicion, he said.

According to the text of Arizona's SB 1070, Arizona police will be required to make a reasonable attempt to determine the immigration status of a person with whom they make lawful contact if reasonable suspicion exists that the person is an alien who is unlawfully present in the U.S.

The law also establishes crimes involving trespassing by illegal aliens, hiring or solicitation of day laborers, and transporting, harboring or concealing illegal aliens.

-- Dan Wheat