The group went to federal court in Milwaukee on Monday, to stop prosecutors from continuing their probe into funding of Wisconsin's recall elections.
The conservative Wisconsin Club for Growth and its director Eric O'Keefe claim the investigation is violating their rights to free speech, free assembly and equal protection. In addition to seeking a court order to end the John Doe, the federal lawsuit seeks damages.
Prosecutors and a judge have reportedly been conducting the secret probe for more than a year, examining whether there were illegal ties between campaign offices and third party contributors during recall elections launched in Wisconsin in 2011 and 2012. Gov. Walker survived the recall against him, becoming the first governor to do so.
Investigators apparently decided to initiate the John Doe probe, while some were involved in another. The earlier John Doe looked into activities of aides and associates who worked for Walker while he was Milwaukee County Executive. Several were charged with campaigning on public time.
The federal suit filed Monday to stop the second John Doe comes, as one former Walker aide has decided to allow the courts to release thousands of pages of emails related to the first probe. They have been sealed, until now.
The judge gave Kelly Rindfleisch 30-days to request that the court keep certain information confidential, but Rindfleisch says the process of sifting through all the documents would be too labor-intensive.
The courts will release the emails and other documents on Feb. 19.