The South Dakota Supreme Court on Wednesday revived a state lawsuit that seeks to identify the secret donor who gave $750,000 to the failed 2006 effort to outlaw most abortions in the state.

The high court's unanimous ruling overturned a circuit judge who had thrown out a lawsuit filed by Secretary of State Chris Nelson, who argues that the donor's name should be made public.

A trial must be held to determine whether a corporation set up to make the donation meets the legal definition of a committee that is required to file financial reports covering its attempts to influence the outcome of a ballot issue, the Supreme Court said.

State Rep. Roger Hunt, R-Brandon, who set up Promising Future Inc. to make the donation, referred questions to his attorney, Steve Sanford of Sioux Falls.

Sanford said before a trial is held in circuit court, he will again argue that the case should be thrown out because the way the law is being interpreted violates the free-speech rights of those who set up the corporation.

Nelson said he is pleased the state will get a chance to argue its case in circuit court.

"This is a positive ruling and hopefully one step toward ultimately getting a complete campaign finance report from Promising Future," Nelson said.

"The purpose of the campaign finance law is to let the public know who is putting money into each side of each of the campaigns so the public can take that into account as they are determining which way they are going to vote on each of these issues or candidates," said Nelson, who is in charge of elections in South Dakota.

Hunt set up Promising Future in 2006. It then gave three $250,000 payments to VoteYesForLife.com, the main campaign group promoting the measure that sought to ban abortions.

Hunt, a staunch abortion foe, said the person who donated the money to Promising Future is a South Dakota resident who wants to remain anonymous out of fear of possible violence.

Voters ultimately rejected the 2006 abortion measure 56 percent to 44 percent. A similar measure, also aimed at prompting the U.S. Supreme Court to overturn its 1973 Roe v. Wade ruling that legalized abortion in the nation, was rejected by South Dakota voters in the 2008 election.

After Promising Future refused to identify the donor who gave $750,000, Nelson sought a court ruling to require the disclosure of the donor's identity.

Circuit Judge Kathleen Caldwell last year issued a summary judgment that dismissed the case. The judge ruled that Hunt and the corporation did not have to disclose the donor's identity because the corporation did not meet the definition of ballot question committee in the version of law in effect in 2006.

Hunt had argued that the state's interpretation of the law required disclosure based on the secretary of state's determination of someone's intent, which could mean spouses or friends would become campaign committees if they merely discussed a ballot issue and agreed to contribute to a campaign.

But the Supreme Court said the issue is whether people become a ballot question committee by forming a corporation that has the sole purpose of making anonymous contributions to ballot issue campaigns.

South Dakota law defines a ballot question committee as "any two or more people who cooperate for the purpose of raising, collecting or disbursing money for the adoption or defeat of any question submitted to the voters at any election," the Supreme Court said.

Caldwell had ruled that Hunt, the unnamed donor and the corporation were involved in contributing, and they did not form a ballot question committee because the legal definition of such a committee does not include the word "contributing."

A judge could find that two or more people were involved and cooperated to provide $750,000 to the ballot issue campaign, the high court said. Their conduct also could be interpreted as raising, collecting or disbursing money, the justices said.

Hunt and the unnamed third party formed a corporation to avoid revealing the donor's identity, the Supreme Court said.

"Therefore, because the unnamed third party would have otherwise been required to reveal his or her identity, the attempted manipulation of the statute fails and summary judgment was improper," Justice Richard W. Sabers wrote for the court.

Attorney General Larry Long said the Supreme Court did not make a final ruling on whether Promising Future has to reveal the anonymous donor. But the high court said the state deserves a trial to settle the question because it's possible that the corporation was a ballot question committee, he said.

Hunt also argues that requiring the disclosure of the donor would violate the First Amendment protection of free speech, but the South Dakota Supreme Court said it would not deal with that argument because the circuit judge did not rule on it.

Sanford said a U.S. Supreme Court ruling in a Wisconsin case last year could mean that the South Dakota law and the way it is being interpreted violate the First Amendment.

The nation's highest court said federal and state governments cannot determine whether speech is legal or criminal based on an interpretation of the speaker's intent or motive, Sanford said. Campaign donations are political speech, and the South Dakota law is being interpreted according to the intent under which Promising Future was created, he said.

Nelson said Hunt and Promising Future should be required to identify the donor even though it's been two years since the 2006 election.

"I would say just because you can tie something up in court long enough doesn't mean you don't have a reporting requirement and shouldn't be required to provide the information you were required to in 2006," the secretary of state said.