The Wisconsin Supreme Court has ended a probe into Scott Walker's 2012 recall election campaign, sparing the Wisconsin governor a political headache just as he launches his bid for the White House.

The court found that Walker's campaign had not illegally collaborated with outside conservative groups three years ago when the governor faced a recall election following labor backlash over his push to weaken public sector unions.

At question was whether Walker's campaign had pushed donors to give to the Wisconsin Club for Growth, which was helping him defeat the recall effort — the alleged collusion was termed the "John Doe" investigation. Walker's attorneys, however, countered that any push had happened before Walker officially became a candidate, and therefore no laws were broken.

The investigation had been hung up for 18 months after a lower court ruling. Walker had maintained innocence even after a separate "John Doe" investigation resulted in six convictions involving embezzlement and money-laundering by former staffers and other connected people from Walker's time as county executive in Milwaukee and his gubernatorial campaign.

A spokeswoman for Walker's campaign told the Milwaukee Journal Sentinel that the ruling "confirmed no laws were broken."

"It's time to move past this unwarranted investigation that has cost taxpayers hundreds of thousands of dollars," AshLee Strong said.

The Sentinel highlighted key passages in the 4-2 decision in favor of Walker, where the majority justices found that no laws were broken, in part because the state's campaign finance laws were "unconstitutionally overbroad and vague."

"To be clear, this conclusion ends the John Doe investigation because the special prosecutor's legal theory is unsupported in either reason or law," Justice Michael Gableman wrote. "Consequently, the investigation is closed."

The court's dissenters wrote that the majority had loosened campaign finance rules until "Anything Goes."

"The majority opinion adopts an unprecedented and faulty interpretation of Wisconsin's campaign finance law and of the First Amendment," wrote Justice Shirley Abrahamson. "In doing so, the majority opinion delivers a significant blow to Wisconsin's campaign finance law and to its paramount objectives of 'stimulating vigorous campaigns on a fair and equal basis' and providing for 'a better informed electorate.' "

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