"On Friday a Wisconsin judge struck a major blow for free political speech when he quashed subpoenas to conservative groups..."

"... and ordered the return of property to the targets of a so-called John Doe campaign-finance probe," write the editors of The Wall Street Journal, who got access to the judge's secret opinion. Judge Gregory A. Peterson wrote that the subpoenas "do not show probable cause" that the targeted conservative groups —  Friends of Scott Walker, Wisconsin Manufacturers & Commerce Inc., the Wisconsin Club for Growth, and Citizens for a Strong America — "committed any violations of the campaign finance laws." The judge, as the WSJ puts it, "bluntly rejects the prosecutor's theory of illegal coordination between the groups and the Walker campaign."

Wisconsin's campaign finance statutes ban coordination between independent groups and candidates for a "political purpose." But a political purpose "requires express advocacy," the judge wrote, and express advocacy means directly advocating the election or defeat of a candidate.

"There is no evidence of express advocacy" and therefore "the subpoenas fail to show probable cause that a crime was committed," Judge Peterson wrote. Even "the State is not claiming that any of the independent organizations expressly advocated" for the election of Mr. Walker or his opponent, he added. Instead they did "issue advocacy," which focuses on specific political issues.

This means that prosecutors essentially invented without evidence the possibility of criminal behavior to justify the subpoenas and their thuggish tactics. At least three targets had their homes raided at dawn, with police turning over belongings, seizing computers and files, and even barring phone calls.

The judge's order vindicates our suspicion that the John Doe probe is a political operation intended to shut up Mr. Walker's allies as he seeks re-election this year....

Democrats would love to intimidate and muzzle the local activists who rallied to Mr. Walker's recall defense.