The 7th Circuit U.S. Court of Appeals released more documents in the case on Friday, including four that were not supposed to be made public.
The documents contained parts of emails from Gov. Walker's 2012 recall campaign team. They instructed him to tell donors to give money to a conservative group that would run ads on his behalf and distribute cash to other groups.
Laws limit how much money individuals can give to campaigns, but there are no restrictions on giving to third parties, and donors can remain confidential. There are also restrictions governing coordination between campaigns and independent groups.
The John Doe probe had been examining whether Walker's campaign illegally coordinated with third party organizations during Wisconsin's recall elections.
Federal Judge Rudolph Randa ordered a halt to the investigation this summer, saying from what he has seen, the parties did not violate election law. Federal appeals court is deciding whether to overrule or uphold Randa's decision about the probe's status.
In the meantime, the court has allowed some documents in the secret investigation, to be released publicly.
The four mistakenly posted online Friday were removed, after a brief period.
Two unnamed entities involved have now asked the appeals court, not to release any further filings, stating that disclosure, "caused real harm to real people."