[JURIST] The city of Tucson, Arizona [official website] has joined a lawsuit against the the state's new immigration law [SB 1070 text; JURIST news archive], a court filing [answer, PDF] revealed Tuesday. Tucson was originally named as a defendant along with Arizona Governor Jan Brewer (R) [official website] in the federal lawsuit [complaint; JURIST report] filed in April by Tucson police officer Martin Escobar. However, the city responded by filing a crossclaim [FRCP Rule 13 text] against Brewer seeking an injunction to prevent enforcement of the law, which is set to go into effect July 29. The city argues that the Arizona law violates the Commerce Clause and Fourth Amendment [Cornell LII backgrounders] of the US Constitution [text], in addition to federal immigration law, through which the federal government has "fully occupied" the field of immigration control. In outlining its Commerce Clause objections, the city explained:

The Act establishes … that for a person who is stopped, detained or arrested, there is a presumption that person is not an alien unlawfully in the United States if the person produces an Arizona driver's license. For persons from New Mexico and other states where proof of citizenship is not required for a driver's license, there is no such presumption. Persons with New Mexico or other out-of-state licenses engaged in interstate commerce are thus required by the Act to obtain and carry additional documentation such as a passport or birth certificate, proving that they are citizens or lawful aliens. Such documentation is not normally carried by all persons engaged in interstate commerce. … The imposition of a burden on out-of-state commerce and a preference for in-state commerce discriminates against interstate commerce and violates the commerce clause of the United States Constitution.

Additionally, the city sought the injunction based on the provision of the Arizona law that would allow any person to bring suit against a city that does not exercise immigration controls to the fullest extent allowed by federal law. The city alleged that fulfilling this burden would divert funding from other law enforcement functions due to budgetary restrictions, delegating the city's police power and prosecutorial discretion to private citizens and causing irreparable injury.

Last week, Brewer said that she will not seek the assistance [JURIST report] of state Attorney General Terry Goddard (D) [official website] in defending against challenges to the new immigration law. Brewer cited a provision in the new immigration bill that gives her authority to seek the assistance of outside counsel rather than the assistance of the attorney general in defending the bill. Several lawsuits have been filed in response to the bill, which was signed into law [JURIST report] at the end of April. The American Civil Liberties Union [advocacy website] filed suit [complaint, PDF; JURIST report] last month, challenging the constitutionality of the law and seeking an injunction, though some find the law constitutional on its face [JURIST op-ed]. Proponents of the law argue that it will discourage illegal immigration, while opponents contend it will lead to discriminatory police practices based on race. The Obama administration, though supporting immigration reform, has sharply criticized the law [JURIST report], calling it "misguided" and expressing concern that it could be applied in a discriminatory fashion. These criticisms are shared by Mexican President Felipe Calderon [official website, Spanish] who called the law a "violation of human rights" [JURIST report]. In May, a group of UN experts found that the law could violate international standards [JURIST report] that are binding on the US.