One of the fusses going around about the new law in Arizona is that it will place an undue burden on residents to carry documentation at all times. Specifically, the argument is made that a driver's license will not be acceptable documentation of legal presence in the US. The new law does provide for the use of federal-, state-, or locally-issued identification as a means of establishing legal presence, as long as (per the text of the bill, SB 1070 Sec 2, amending ARS 11-1051B(4)) this ID "requires proof of legal presence in the United States before issuance."
So, how many states' driver's licenses require proof of legal presence (PLP) before issuance? All but two, New Mexico and Mississippi. (Technically New Hampshire also does not require PLP, but they also appear only to issue driver's licenses to US citizens - mooting the question.) New Mexico does have a weak form of PLP confirmation, in that a Mexican consular card or an ITIN card are acceptable as part of the identity confirmation process. Mississippi's process seems remarkably incomplete, given the near-universal PLP requirements elsewhere in the country. In the end, New Mexico is likely to be the most problematic jurisdiction in terms of its interaction with Arizona's new law, with the two states sharing a border.
(To note, some states have only very recently enacted laws requiring PLP documentation, potentially complicating the validity of their licenses in the near term. Others, probably most others, have had PLP verification in place for at least several years - California first enforced PLP requirements in 1994, for example. Regardless of the tenure of the PLP requirements, as the renewal cycles of existing licenses turn over, the transient consideration of date of enactment will become irrelevant.)
The following is a list of all forty-eight states whose driver's licenses should be acceptable under AZ SB 1070, linked to their respective webpages describing proof-of-legal-presence documentation requirements for driver's licenses. States with recently-enacted PLP laws are noted separately.
AK AL AR AZ CA CO CT DE FL GA
IA ID IL IN KS KY LA MA ME MI MN
MO MT NC ND NE NJ NV NY OH OK
OR PA RI SC TN TX VT WA WI WV WY
HI - See 'General Requirements' sections (c) & (d)
MD - Current law effective 1 Jun 2009
NH - NH appears not to issue licenses/IDs to immigrants/visitors; a NH license thus indicates citizenship
SD - Current law effective 31 Dec 2009
UT - Current law effective 1 Jan 2010
VA - Follow questionnaire form to see requirements
States with driver's licenses likely without acceptable PLP verification under AZ SB 1070: