Thomas said he reviewed a legal memo prepared by members of Los Abogados, an association of Hispanic attorneys, which concluded that Patrick Haab broke state law in the April 10 incident. That report, released in detail Monday, said Haab committed aggravated assault.

But Thomas said he remains convinced he is right.

"Our office reviewed the law and the facts in that case extensively," he said. "We came down where we came down."

He said attorneys can disagree on the law, as evidenced by the 5-4 decisions of the U.S. Supreme Court. But Thomas said he is sticking by his conclusion that Haab was conducting a valid citizen's arrest.

Antonio Bustamante, a member of the Los Abogados board, acknowledged that Arizona law does permit individuals to arrest people who are committing felonies. But Bustamante said federal immigration laws specifically say they can be enforced only by federal agents or local police, and not by individuals.

Thomas would not specifically answer that question. But he said his own agency's legal research is sound.

"We analyzed it in good faith," he said. "And that's where we came down."

Bustamante said the refusal to prosecute Haab sets a bad precedent.

"What Patrick Haab has done -- and the decision of the county attorney has encouraged -- is the continuing demonization of undocumented people," he said.

"If one can continue to think that their very presence in the country is somehow something that makes them 'illegal,' that they're 'criminals,' then it continues to allow people to think it's OK to point guns at them and take them into custody," Bustamante continued.

He said that crossing the border illegally is only a misdemeanor, as is remaining in this country for more than 30 days without registering with federal authorities.

Bustamante called Thomas' statement "irresponsible." He said there is no way the county attorney could have reviewed his organization's legal treatise in the 45 minutes between when it was delivered and when Thomas said he would not change his mind.

Haab was arrested by Maricopa County sheriff's deputies after the incident at a rest stop on Interstate 8 southwest of Phoenix. Haab initially told deputies he drew his gun to protect himself.

Thomas said it turned out that one of the men was a coyote, smuggling others into this country illegally. He said human smuggling is a felony -- and that the individuals the coyote was smuggling were also felons because they were involved in an illegal conspiracy.

Paul Charlton, the U.S. Attorney for Arizona, said entrants can't be charged under federal law with conspiring to smuggle themselves. Charlton also was critical of Haab's actions.

"Mr. Haab's actions risked the lives of the illegal aliens he detained," Charlton said. "He risked his own life, and had law enforcement officers come upon that scene not knowing what was happening, he could have risked everyone's life."

Charlton said a preliminary review of the case found no federal laws that Haab may have violated. But Charlton said he forwarded the entire file to the U.S. Department of Justice for review to see if there were breaches of federal civil rights laws.