MADISON, Wis. -

The investigation into Gov. Scott Walker's 2012 recall campaign and conservative groups that supported him has been halted for the second time in as many days by a federal judge.

U.S. District Judge Rudolph Randa on Thursday issued an order in a separate case that allows for his previous order halting the probe to be effective.

A federal appeals court on Wednesday had said Randa's original order Tuesday stopping the investigation was in error because he had yet to rule on whether a separate appeal by prosecutors was frivolous.

Randa said Thursday that the appeal, which was to his ruling that prosecutors are not immune from being sued by Wisconsin Club for Growth, was indeed frivolous. That reinstates his preliminary injunction halting the probe.