Advocacy groups promised to challenge the sweeping measure, which like Arizona’s law also allows police to arrest anyone suspected of being an illegal immigrant if the person is stopped for some other reason. In addition, it requires all businesses to check the legal status of workers using a federal system called E-Verify.

“It is clearly unconstitutional. It’s mean-spirited, racist, and we think a court will enjoin it,” said Mary Bauer, legal director for the Southern Poverty Law Center.

It takes effect Sept. 1.

Republican Gov. Robert Bentley, who signed it into law Thursday, expressed confidence it would withstand any legal challenges.

“We have a real problem with illegal immigration in this country,” he said. “I campaigned for the toughest immigration laws, and I’m proud of the legislature for working tirelessly to create the strongest immigration bill in the country.” Alabama has an estimated 120,000 illegal immigrants, a nearly fivefold increase from a decade ago, according to the Pew Hispanic Center. Many of them are believed to be working on farms, at chicken processing plants and in construction.

Alabama’s Hispanic population more than doubled between 2000 and 2010 to 186,000, or 3.9 percent of the state’s nearly 4.8 million people, according to the Census. Figures were not available on their legal status.

One of the legislation’s sponsors, Republican Sen. Scott Beason, said it would help the unemployed by preventing illegal immigrants from getting jobs in the state.

Alabama’s unemployment rate stood at 9.3 percent in April, the most recent figure available.

“This will put thousands of Alabamians back in the work force,” Beason said.

The Alabama Business Council has not taken a public stand on the law. In neighboring Georgia, some farmers and business owners warned that a crackdown passed recently in that state would make it more difficult to hire the laborers they rely on - many of whom are illegal immigrants.

The Alabama measure instantly puts the state at the forefront of the immigration debate. Organizations such as the American Civil Liberties Union and the Southern Poverty Law Center agreed that it is the nation’s toughest crackdown on illegal immigration.

Linton Joaquin, general counsel for the National Immigration Law Center in Los Angeles, said the Alabama law covers all aspects of an immigrant’s life.

“It is a sweeping attack on immigrants and people of color in general. It adds restrictions on education, housing and other areas. It is a very broad attack,” Joaquin said.

Among other things, the law makes it a crime for landlords to knowingly rent to an illegal immigrant.

Another provision makes it a crime to transport a known illegal immigrant. Arizona’s law appears narrower: It includes language against human smuggling and makes it illegal to pick up laborers for work if doing so impedes traffic.

Alabama’s law also goes further in requiring schools to check the immigration status of their students. The measure does not prohibit illegal immigrants from attending public schools; lawmakers said the purpose instead is to gather data on how many are enrolled and how the much the state is spending to educate them.

Jared Shepherd, an attorney for the ACLU, warned that because of that provision, some immigrant parents may not send their children to school for fear of arrest or deportation.

Alabama’s measure was modeled on Arizona’s. A federal judge blocked the most controversial parts of Arizona’s law last year after the Justice Department sued. The case appears headed to the US Supreme Court.

A less restrictive law in Utah also was blocked after a lawsuit was filed. Civil liberties groups have sued to stop Georgia’s law as well.