Birmingham, Alabama (CNN) -- Attorneys squared off in federal court Wednesday over Alabama's controversial new immigration law, which could become the toughest in the nation.
Opponents of the measure -- including state church leaders, the U.S. Justice Department and the American Civil Liberties Union -- are asking a judge to stop the law, which is scheduled to go into effect September 1. State officials argue that the law will help Alabama and won't violate civil rights.
U.S. District Judge Sharon Blackburn did not rule at the end of Wednesday's daylong hearing. But she repeatedly questioned lawyers about their arguments against the law, at times saying she did not agree with their positions.
The Alabama law requires that police "attempt to determine the immigration status of a person who they suspect is an unauthorized alien of this country," according to an Alabama House of Representatives fact sheet. That provision is similar to other laws aiming to crack down on illegal immigration passed by state legislatures over the past year.
But the Alabama law also includes more expansive measures, including requiring the state to check immigration status of students in public schools.
An attorney for the Southern Poverty Law Center Wednesday argued that portion of the law was unconstitutional.
Alabama Attorney General Luther Strange stressed Wednesday that the law would not prevent undocumented immigrants from having access to public-school education.
Strange also argued that the law was not an anti-immigrant measure, and that the state welcomes visitors.
Earlier this month leaders from the Episcopal, Methodist and Catholic churches of Alabama sued the state's governor, its attorney general and a district attorney over the law.
One attorney representing bishops said in court Wednesday that representatives of the church did not want to become immigration agents, arguing that the law would make church officials targets for ministering to illegal immigrants.
A U.S. Department of Justice attorney argued that the federal government, not individual states, should control immigration enforcement.
Alabama Gov. Robert Bentley signed the law in June.
"Gov. Bentley campaigned on the need for a strong immigration bill," Bentley's spokeswoman Rebekah Mason said last month.
Republican Alabama state Rep. John Merrill told CNN in June that the legislation is "good for Alabama" because it will reduce illegal immigration to the state and "provide equal opportunities for all people who want to come to Alabama legally."
ACLU attorney Andre Segura noted that the length of Wednesday's hearing showed the complexity of Alabama's law compared with other state measures.
State Sen. Scott Beason, a co-sponsor of the law, said he was pleased with how Wednesday's proceedings went. The judge was fair in her questioning, he said, adding that he was confident the law would be upheld.
CNN's Gustavo Valdes in Birmingham contributed to this report.