A federal judge has refused to block the state investigation of a conservative Montana political group, which is accused of illegally concealing donors that financed three ballot measures in 2006.

U.S. District Judge Richard Cebull of Billings said claims by Montanans in Action that the investigation is violating its constitutional rights can be argued in state court at the appropriate time.

The federal court doesn't need to be involved at this point, he said in an order issued Wednesday.

"It is not the place for federal courts to give constitutional scrutiny to ongoing state administrative proceedings," Cebull wrote. "To that end, (the group's) claims are premature."

Montanans in Action, based in Lewistown, distributed nearly $1.2 million to the campaigns of three ballot measures in 2006, including one to limit state spending.

State Political Practices Commissioner Dennis Unsworth is investigating a 2006 complaint filed by a rival group, which says Montanans in Action must reveal its financial donors.

Leaders of Montanans in Action have said the law doesn't require the group to reveal its monetary supporters, because it's a nonprofit political/education group.

In late 2006, the group filed suit in U.S. District Court to block Unsworth's investigation, saying the query is violating the group's First Amendment rights of free speech and political association.

Trevis Butcher, the group's treasurer, has said the investigation is preventing MIA from carrying out plans that would show it's more than just a campaign-fund conduit.

Unsworth's office is investigating a complaint that says Montanans in Action acted only as a conduit for campaign funds in 2006, thus requiring it under Montana law to identify its financial backers.

Edward Greim, a Kansas City, Mo., attorney representing Montanans in Action, said Thursday that Wednesday's federal court ruling simply directs the group to make its constitutional rights-violation claims in state court.

The federal judge said state law gives Montanans in Action ample opportunity to ask a state judge to review whether its rights are being violated by Unsworth's investigation or its ultimate results.

"(The order) has sort of laid out a process for doing that," Greim said. "We're confident these constitutional claims are meritorious, and we'll bring them in any forum we need to."

Cebull also did not dismiss Montanans in Actions' claim for damages -- should a court find that the group's rights were violated.

Greim said if the group eventually wins a ruling that its constitutional rights were violated, it could come back to the federal court and attempt to prove it deserves monetary damages.

Unsworth could not be reached for comment Thursday.

Montanans in Action in 2006 financed ballot measures to limit state spending, allow the attempted recall of judges for any reason, and protect certain property rights. All three measures were tossed from the ballot because of signature-gathering fraud.

Butcher has said a nonprofit foundation, which he declined to name, has helped pay for MIA's lawsuit in federal court.