PHOENIX — A federal judge will allow challengers to Arizona’s major law targeting illegal immigration to see what advocacy groups were advising legislators in emails, letters and memos while the law was written. The challengers are looking for any indication of racial bias.

U.S. District Judge Susan Bolton rejected arguments by the Federation for American Immigration Reform and the Immigration Reform Law Institute that the messages they sent to lawmakers who crafted and supported SB 1070 are private. Bolton also said that communications from legislators to either group cannot be shielded from public view, either.

The ruling is a significant victory for those who have been working since the law was enacted in 2010 to have it — and especially its “papers, please” provision — declared unconstitutional.

That’s because the lawsuit is based in part on claims that the Legislature acted in a way to purposely discriminate against Hispanics and other minorities, violating the Equal Protection Clause of the U.S. Constitution.

Victor Viramontes of the Mexican American Legal Defense and Educational Fund said those communications could prove that the real intent was racial bias and not simply a bid to help the federal government enforce laws against illegal immigration.

SB 1070 contained a variety of measures aimed at giving police more power to detain people they believe are in the United States illegally.

Several of those sections were voided by the U.S. Supreme Court, including making it a crime for an illegal immigrant to apply for work in a public place and allowing police to arrest someone in this country illegally for failing to carry federally issued immigration cards.

But the justices refused to set aside another provision that requires police to try to determine the immigration status of someone they have already stopped if there is “reasonable suspicion” that person is unlawfully in the country. The court said there was no reason to believe that, as written, the measure is pre-empted by federal law.

What the high court never addressed — and what remains in front of Bolton — is a separate question of whether the provision violates the equal protection rights of minorities. That, Viramontes said, requires proof of “racial animus.”

“You look at what legislators were saying around the time that they passed the law, and what people who were talking to legislators were saying around the time that the law was passed,” he said.

“Here, you have prominent proponents of SB 1070 talking to each other,” Viramontes continued. “And we would like to know what they said to each other.”

Challengers are clearly looking for evidence of racial intent. The subpoenas specifically ask for communications with words like “alien,” “day laborer,” “illegals,” “Mexican,” “profiling,” “Spanish,” “undocumented” and “wetback.”

Attorneys for the two groups told Bolton the subpoenas would interfere with their First Amendment rights to communicate with legislators.

But the judge said nothing in the request interferes with that right. She there is nothing in law that “protects from public view communications with public officials in their official capacity about a matter of public concern.”

Anyway, Bolton said, communications to public officials are public records under Arizona law. The challengers are seeking them from the two groups because the Legislature routinely destroys emails after 90 days.

The judge also rebuffed contentions that the communications are irrelevant, noting that challengers have to show “proof of racially discriminatory intent or purpose in the enactment of SB 1070.” That, she said, requires an inquiry into not only the purpose of the law as stated publicly by sponsors but a look at “circumstantial and direct evidence of intent as may be available.”

And Bolton ruled that the communications sought are likely to contain admissible evidence themselves or, at the very least, lead to the discovery of evidence of legislative intent.

Bolton also dismissed claims by the two groups that they were providing legal advice to lawmakers, something generally off-limits to disclosure. She said the evidence shows no evidence of a formal attorney-client relationship, saying the groups “were offering policy — not legal — advice.”

More is at issue than just the future of the ability of police to detain and question those suspected of being in this country illegally.

Still being litigated are several other provisions of SB 1070 that never made it to the Supreme Court, though a federal appeals court has blocked them from being enforced while the case plays out in Bolton’s court.

One makes it a crime for someone looking for work to enter a car stopped on the street. It also criminalizes drivers who stop to pick up laborers.

Another makes it illegal under state law to knowingly transport or harbor those in this country illegally.

Bolton’s ruling covers more than just the communications about SB 1070. Challengers also want to see emails and other documents related to crafting various other prior measures dealing with illegal immigration in the years before SB 1070 was adopted.

“It is reasonable to conclude that the intentions behind those bills were similar, if not identical, to the intentions behind SB 1070,” Bolton wrote. She called them “part of the historical background” of the enactment of SB 1070 and therefore relevant.