MADISON, Wis. (AP) — A federal judge's decision to halt a secret investigation into illegal coordination between conservative groups and Republican Gov. Scott Walker's recent recall campaign could have far-reaching implications for campaign finance law. U.S. District Judge Rudolph Randa on Tuesday ordered prosecutors to halt their investigation. That order was put on hold Wednesday by an appeals court. The 7th Circuit Court of Appeals in Chicago said Randa should not have issued the order without waiting for it to decide another appeal in the case. Prosecutors leading the secret probe say if his decision stands, it would allow independent groups that don't have to disclose their donors to collaborate with candidates who do. Candidates would then have access to vast amounts of money without voters ever knowing the source. WisPolitics.com editor J.R. Ross told AM 1170 WFDL's Between the Lines program the case could go all the way to the U.S. Supreme Court.