PHOENIX — Attorneys for immigrant-rights groups asked the U.S. Supreme Court on Monday to rebuff a last-ditch attempt by the state to start prosecuting people for harboring and transporting those not in the country legally.

Attorney Omar Jadwat of the American Civil Liberties Union said it is clear that the provision of a 2010 Arizona law aimed at illegal immigration is pre-empted by federal law. He said the language goes far beyond what Congress considers acceptable.

The law in question makes it illegal for someone to transport, conceal, harbor or shield anyone unlawfully present in this country or “encourage or induce the alien to come to or live in Arizona.’’

It is part of SB 1070, a broader package of measures designed to give police more power to question and detain those they believe are in the country illegally. Several provisions already have been voided by courts, including three by the Supreme Court itself, as pre-empted by federal law.

John Bouma, attorney for Gov. Jan Brewer, asked the high court to let Arizona enforce the law after both a trial judge and the 9th U.S. Circuit Court of Appeals blocked its enforcement.

Bouma argued that there is nothing improper about the state having its own laws aimed at controlling immigration. And he said the fact that there are federal laws criminalizing the same conduct does not pre-empt state action.

But Jadwat said the Arizona measure is not a mere parallel of federal statute.

“(The law) directly undermines federal law by imposing criminal penalties on conduct that Congress elected not to punish, creating additional and different penalties not contemplated by federal law,’’ he wrote. In any event, even where Arizona law overlaps federal harboring laws, it divests federal authorities of “exclusive power to prosecute these crimes.’’

One question the high court will need to decide is if anyone is in danger of actually being prosecuted under state law.

Strictly speaking, the case before the court is not on the merits of the Arizona law. Instead, it is on an injunction originally issued by U.S. District Court Judge Susan Bolton blocking its enforcement while she considers the merits of the arguments.

That case is ongoing in her Phoenix courtroom.

But to get an injunction, federal court rules require not just a showing by the challengers that they are likely to ultimately win but that they also show they are in danger of being harmed by the law. Bouma contends no one has shown such a risk, meaning they have no standing to seek an injunction.

One of the plaintiffs is pastor Luz Santiago of Mesa.

Jadwat noted that the Court of Appeals found that her ministry helps provide food, shelter and transportation “to a congregation that includes many individuals she believes to be unauthorized immigrants.’’ He said that certainly puts her at risk of being prosecuted by state officials.

And Jadwat said that also applies to many of the organizations that also have sued to block enforcement, including Southside Presbyterian Church, Border Action Network and Arizona South Asians for Safe Families. He said many of these groups’ “core activities’’ involve transporting or seeking shelter to those not in the country’’ legally.

The question for the high court could go deeper than whether the Arizona law simply parallels the federal statute. There’s also the question of who gets to determine who is in this country legally.

Karen Tumlin, attorney for the National Immigration Law Center, said there needs to be a determination by a federal judge that someone is not authorized to be here before anyone else can be prosecuted under federal anti-harboring laws. But she said the contested provision of SB 1070 essentially gives that chore to state judges.

The high court has not decided whether to hear Arizona’s appeal or simply leave the lower court injunctions in place.