A federal judge on Monday asked tough questions about the potential fallout from Georgia’s new anti-illegal immigration law but said he would rule later on whether it should be halted.

Many of the legal arguments for and against the Arizona-style law revolve around whether it is constitutional. But during a hearing Monday, U.S. District Court Judge Thomas Thrash repeatedly focused on the law’s practicality. He questioned its purpose, suggested it would not be enforced consistently across state’s 159 counties and said local authorities could pick and choose who to target with it, favoring some people and not others.

Thrash, who was nominated to the court by President Bill Clinton, offered one hypothetical example in which local authorities could target immigrants to get them out of their public schools but not touch the immigrant cook who works at the popular Mexican restaurant in town. The judge also questioned whether teenage U.S. citizens should be prosecuted for driving their illegal immigrant parents to the grocery store.

Based on Thrash’s line of questioning, the Republican author of the law said Monday he wouldn’t be surprised if the judge grants opponents of the law a preliminary injunction and halts the measure. But Rep. Matt Ramsey,R-Peachtree City, said he was confident the state would appeal to the 11th U.S. Circuit Court of Appeals in Atlanta and win.

“We believe in the end that the law -- on its merits -- is going to be found constitutional -– all provisions of the law,” Ramsey said.

Thrash said he plans to issue his decision on whether the law will be halted before July 1, when much of the law is scheduled to take effect.

Signed by Republican Gov. Nathan Deal last month, the law empowers local and state police to investigate the immigration status of certain suspects and arrest illegal immigrants and take them to state and federal jails. It also would require many businesses to use the federal E-Verify program to ensure their new hires are eligible to work in the United States. And it would punish people who -- while committing another crime -- knowingly transport or harbor illegal immigrants or encourage them to come to Georgia.

The American Civil Liberties Union, the National Immigration Law Center and several other civil and immigrant rights groups asked the judge Monday to put the law on hold, pending the outcome of a lawsuit they have filed to challenge its constitutionality. They say the law would interfere with the federal government's authority to set and enforce immigration policy, promote racial profiling and violate the Fourth Amendment by allowing police to detain people for inordinate periods of time while investigating their immigration status.

Federal judges have put similar laws on hold in Arizona and Utah following court challenges.

Senior Assistant State Attorney General Devon Orland defended Georgia's law in court Monday. She had just begun testifying when Thrash started asking her a series of pointed questions about the purpose of the law and its practicality. At one point, he declared “immigration has traditionally been a matter for federal regulation, not local law enforcement.”

“Is the purpose to drive all undocumented immigrants out of Georgia?” he asked Orland. He then referred to the immigrants who work in some of Georgia’s largest industries, including farming, chicken processing and carpet manufacturing.

Orland responded that illegal immigrants are costing the state millions of dollars by burdening its jails and hospitals at a time of high unemployment.

“Just because we economically depend on something that is unlawful does not change it from unlawful to lawful,” she told the judge about illegal immigrants working in Georgia. She later said: “This doesn’t change anything. Illegal is illegal is illegal.”

Thrash asked Orland whether an 18-year-old U.S. citizens should be prosecuted for driving his illegal immigrant mother to the grocery store. Orland responded that the law is sometimes harsh but that “does not make it unconstitutional.”

The attorney general’s office declined to comment after the hearing. But a spokesman for the governor said: “This law was carefully tailored to conform with existing federal law and with the rulings of federal courts.”

Supporters of the law say they are confident that at least the part of the law requiring the use of the federal E-Verify program will withstand the court challenge. They said that is the most important provision of the law because it could discourage illegal immigrants from coming to Georgia to find jobs. Last month, the U.S. Supreme Court upheld an Arizona law that requires companies to use the federal work authorization program.

Attorneys for the ACLU and National Immigration Law Center said they didn’t want to read too much into Thrash’s tough questions but said they were cautiously optimistic he would rule in their favor.

“He clearly understands that there are constitutional issues at stake,” said Karen Tumlin, a managing attorney for the National Immigration Law Center. “It was very telling when he said, ‘So, we are going to have 159 different immigration enforcement schemes.’”

Staff Writer Craig Schneider contributed to this report.