ST. PAUL (AP) — The future of a new Minnesota law that let the public know about polarizing political donations from Target Corp., Best Buy Co. and other companies rests with a federal judge who will decide whether to suspend the disclosure requirement on free speech grounds.

U.S. District Judge Donovan Frank said Friday he will rule within a month on a request for a temporary injunction to suspend the law, which could free corporations and other independent groups to spend on this year’s election without revealing their identities. Abortion opponents Minnesota Citizens Concerned for Life, the anti-tax Taxpayers League of Minnesota and a travel agency brought the lawsuit last month.

Their attorney, Joe La Rue of Terre Haute, Ind., said Minnesota’s disclosure requirements for independent spending are so onerous that they amount to an unconstitutional ban on free speech. Under a law that took effect June 1, Minnesota makes corporations and other independent political groups register with state campaign finance regulators. They’re also required to file public reports naming their donors and itemizing their expenditures five times this year.

“These are the burdens that the Supreme Court said you cannot put on people who want to exercise their free speech rights,” La Rue said during a three-hour hearing.

State Solicitor General Alan Gilbert said the law doesn’t block corporations and independent groups from spending unlimited amounts, as long as they disclose their spending. He said the public debate over Target’s donation shows that the law works.

Under the new law, a business-oriented political fund called MN Forward collected more than $1 million since June, including $150,000 from Target. When MN Forward disclosed its donors as required twice last month, Target became the focus of a national backlash from liberals and gay rights supporters because of MN Forward’s support for Republican gubernatorial candidate Tom Emmer, a vocal gay marriage opponent.

“The public has a compelling interest in information regarding sources of political spending so they can make informed decisions in the political marketplace,” Gilbert said.

The Legislature unanimously passed the disclosure law after a recent U.S. Supreme Court ruling allowed corporations to spend company funds directly on elections, wiping away prohibitions on corporate campaign spending in Minnesota and about half the states. The statute applies to independent expenditures, or those made without a candidate’s input or knowledge.

In Target’s case, the company wasn’t required to disclose the donation, but MN Forward was. But the new law allows companies themselves to spend on campaigns if they register and follow the disclosure requirements.

La Rue said the law requires corporations to account separately for such political spending, violating their right to spend general corporate funds on elections.

Frank interrupted the attorneys frequently with technical questions, at one point asking both sides whether a temporary injunction would mean the end of disclosure for this election cycle.

Assistant Hennepin County Attorney Dan Rogan said lifting the law could lead to a flood of corporate money into the election in October, without voters knowing who was behind the messages. Minnesotans will elect a new governor and the entire Legislature in November.

If the law is struck down, the earliest that the Legislature could replace it would be next year.