... The Wisconsin Supreme Court's decision to close the case is a legal victory for Gov. Scott Walker.

This post has been updated. 

MANCHESTER, N.H. — The Wisconsin Supreme Court on Thursday closed a controversial criminal investigation into whether Gov. Scott Walker's 2012 campaign illegally coordinated with outside conservative groups, clearing a potentially prickly legal hurdle for Walker that has cast a shadow on his presidential campaign.

The decision, which is the culmination of years of legal maneuvering and speculation, comes three days after Walker formally announced his White House bid. The newly-minted presidential candidate is here in New Hampshire Thursday, part of a multi-day swing through the early voting states to launch his campaign.

The case dates back to the tumultuous 2012 recall election that began after the Wisconsin governor escalated his efforts to stymie public collective bargaining in the state. Walker was ultimately able to survive that turbulent recall fight, which spanned parts of 2011 and 2012 -- but in the time since, his campaign has been accused of illegally coordinating with conservative outside groups such as the Wisconsin Club for Growth on spending and fundraising.

The "John Doe" probe -- as investigations of its type are called in Wisconsin because of rules preventing involved parties from speaking publicly about proceedings -- could have led to deeper scrutiny into Walker’s 2012 campaign practices and possible release of documents related to the case. More immediately, it could have left an sense of impropriety hanging over the governor’s recall victory.

The decision involved three pieces of litigation. On issues related to campaign finance, the state Supreme Court ruled 4 to 2. Justice Michael J. Gableman, who wrote for the majority, stated that the state's campaign finance laws are "unconstitutionally overbroad and vague" and, if enforced as prosecutors have suggested, would result have resulted in the "chilling of otherwise protected speech" for political advocates.

Gableman wrote critically of how prosecutors and others handled this investigation, noting that search warrants in 2013 were served "in pre-dawn, armed, paramilitary-style raids in which bright floodlights were used to illuminate the targets' homes."

"To be clear, this conclusion ends the John Doe investigation because the special prosecutor's legal theory is unsupported in either reason or law. Consequently, the investigation is closed," Gableman wrote, siding with a previous decision made by a state court judge. Gableman then ordered all parties to "cease all activities related to the investigation, return all property seized in the investigation from any individual or organization, and permanently destroy all copies of information and other materials obtained through the investigation."

In dissenting, Justice Shirley Abrahamson wrote that the majority of the court are adopting an "unprecedented and faulty interpretation of Wisconsin's campaign finance law and of the First Amendment" that ignores the spirit of the law, which seeks to prevent large campaign donations from corroding elections. She called the theme of the majority's opinion "Anything Goes."

"[T]he 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,'" Abrahamson wrote.

Walker's team and other Republicans in the state have long considered this investigation a politically motivated witch hunt against the Wisconsin governor started by Milwaukee County District Attorney John Chisholm, a Democrat. Francis Schmitz, the special prosecutor leading the investigation, has said that he voted for Walker.

"Today’s ruling confirmed no laws were broken, a ruling that was previously stated by both a state and federal judge," said Walker spokeswoman AshLee Strong. "It is time to move past this unwarranted investigation that has cost taxpayers hundreds of thousands of dollars."

During a campaign stop in Amherst, New Hampshire, Walker told reporters that he and his team are pleased with the decision.

“As folks in Wisconsin’s will tell you, I’ve gone through these battles so many times. I don’t get too up or too down, I’m pretty even keeled in all this," he said. "So we’re pleased; it’s just one more thing that allows us to take a step moving forward.”

Wisconsin Club for Growth counsel Todd Graves said in a statement that investigators had "acted like playground bullies without fear of restraint from the courts... We're pleased that the court agrees with the position we've maintained from the time our clients first learned of this improper political investigation."

Several Wisconsin Democrats and liberal activists have criticized the decision, often pointing out that some of the advocacy groups at the heart of this investigation -- including the Wisconsin Club for Growth, Citizens for a Strong America and Wisconsin Manufacturers and Commerce -- spent millions of dollars on the campaigns of the four conservative judges who formed the majority. Schmitz, the special prosecutor, asked one or more of the justices to recuse themselves because of that financial connection, but none agreed to do so.

Jay Heck, the executive director of Common Cause in Wisconsin, called the decision "highly flawed" and recommended that it be appealed to the U.S. Supreme Court.

"Unless it is successfully appealed, the decision could conceivably now lead to unlimited coordination between outside spending groups with candidate committees and effectively render contribution limits meaningless in Wisconsin," Heck said in a statement. "Unlimited money, much or most of it secret and from outside of Wisconsin, could now flow into Wisconsin and be coordinated by candidates with outside groups to influence the outcome of our elections."