PHOENIX — Arizona businesses may not be able to challenge a new law making it illegal to hire undocumented workers unless at least one can show some actual harm from the statute — perhaps by being charged with breaking it.

 At a hearing Wednesday, attorneys for various companies and business groups argued to U.S. District Court Judge Neil Wake only the federal government can punish companies that employ people not in this country legally. They said that makes the new state law to suspend or revoke the licenses of those who are hiring undocumented workers illegal.

 But Wake told them even if he accepts their arguments — something he has not indicated he does — only those who can show some immediate threat of prosecution have standing to ask him to void a state law. And he noted none of the plaintiffs in the lawsuit admits to hiring those not legally permitted to work here.

 The judge also suggested the entire lawsuit may be flawed. He pointed out the legal papers ask him to block Gov. Janet Napolitano and Attorney General Terry Goddard from enforcing the statute. But Wake noted the law gives the actual job of prosecuting errant employers to the 15 individual county attorneys.

 All that could mean that Wake, who has promised to rule before the law takes effect Jan. 1, might never answer the central question of whether Arizona can enact laws to ensure firms hire only citizens and legal U.S. residents.

 The statute approved by the Legislature earlier this year and signed by Napolitano allows a judge to suspend a firm’s ability to do business for up to 10 days if it is found to have knowingly hired an undocumented worker. A second offense within three years results in permanent revocation of all state licenses and permits.

 Attorney David Selden whose clients include the Arizona Contractors Association, the state Chamber of Commerce and Industry, the Arizona Farm Bureau Federation and the Arizona Restaurant and Hospitality Association, said Congress specifically barred states from imposing civil or criminal penalties on firms which hire undocumented workers.

 But Wake pointed out that 1986 federal law permits states to enact “licensing or similar laws.’’

 “Doesn’t that pretty much say there is no preemption for state licensing sanctions laws?’’ he asked. Selden, however, said that exception allows states to deny or revoke licenses only after a federal judge — someone empowered to determine who is legally in this country — decides a company broke the law. Wake scoffed at that explanation.

 “You’re asking the court to add words to the statute that are not there,’’ he said. And the judge was no more impressed by Selden’s argument that Congress would have barred states from imposing fines against offending firms but instead let them impose a “death penalty’’ by putting them out of business. “You’re asking me to tell Congress I’m smarter than them, (that) this was a dumb idea,’’ he said. Wake said federal legislation is always a compromise and “Congress can draw the line (about who gets to enforce what) wherever it sees fit.’’

 Before he let the lawyers argue the legal merits of the new law, he grilled them on whether they have any legal standing to challenge it. He said they provided “no specific threat’’ of having the statute enforced against their clients.  “The only evidence before me is generalized information from relevant public officers saying they intend to enforce the law,’’ Wake said, referring to comments by Maricopa County Attorney Andrew Thomas and Sheriff Joe Arpaio. Jonathan Weissglass, who represents Chicanos Por La Causa, which also sued, said companies already are being harmed because the law also requires them to check the legal status of all new employees through the federal government’s E-Verify program. He said that means not just having a computer and Internet access but the time involved in both training people on the system and running the checks.

 But Mary O’Grady, the state’s solicitor general, pointed out there is no punishment in the law for those firms who refuse to sign up for the E-Verify system. Weissglass countered the penalties come elsewhere. He said companies that refuse to use the federal database will be unable to sign affidavits, required to get some licenses and contracts, that they are in compliance with all state laws.

 He also argued the law still has an element of illegal government coercion because companies which run the computer checks are entitled to a “rebuttable presumption’’ they did not knowingly hire undocumented workers. He said businesses, fearing loss of licenses, will feel compelled to use the E-Verify program.