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In the four years since he left the House of Representatives, where he led legendary impeachment hearings against President Bill Clinton, Bob Barr, the former Georgia Republian congressman, has kept some unlikely company.

Unlike some Republicans who have come to criticize President Bush on the Iraq war only since the 2006 midterm election, Barr has been a constant critic of the president in the face of strident party loyalty.

The American Civil Liberties Union calls the former Republican a 'friend.' Last year, Barr joined Democrats trying to roll back Patriot Act provisions. Currently, he is lobbying for the Marijuana Policy Project.

His critics on the right suggest he's finally gone over to the dark side, but a substantial number of people consider him heroic.

"I think conservatives have always seen Bob as utterly fearless," said Craig Shirley, a veteran Republican media strategist, who called Barr one of the "first voices in the wilderness" for reason during the combined GOP-controlled White House and Congress.

That has not always made him friends among Republicans, but it sure has reached a growing number of disenchanted libertarian conservatives, Shirley added.

"I think there are too many people in the Republican Party today who don't know a whit about why they are in the Republican Party; they don't know conservatism," Shirley said. "There is a strong intellectual libertarian strain that runs through the conservative movement and that's what he represents."

Last year, Barr announced he was leaving the Republican Party to become a libertarian. In doing so, he has given to the Libertarian Party, home to some 240,000 registered voters fighting for limited government and individual freedoms, one of the most recognizable and possibly effective spokespersons in its existence.

"He gives the party a new level of credibility they've never had before," said Chuck Muth, a political consultant and head of Citizen Outreach, a libertarian think tank. "If the Libertarian Party can target angry and disenchanted limited-government Republicans and make a compelling case for them switching over to the Libertarian Party with Barr … they just might be onto something."

Muth said Barr helps the Libertarian Party reach out to those conservatives convinced that neither major party has been true to its principles, and brings a third party movement closer to legitimacy.

"Now if a drug-warrior like Barr can find a way to be comfortable in the Libertarian Party," said Muth, "then a lot of others might now find themselves joining him."

Expanding His Mind

Not more than a decade ago, Barr, a former federal prosecutor, was known for his tough stance on the nation's drug laws and even helped to thwart the District of Columbia's medical marijuana law.

But he has shown time and again that he is open to new ways of thinking, particularly when it brushes up against his constitutional ideals.

"Some very substantial questions have been raised in my mind" about the federal government's jurisdiction over state laws regarding medical marijuana, Barr told FOXNews.com

The U.S. Supreme Court has ruled that the federal ban on pot supercedes state law regarding medical marijuana, but Barr disagrees with that conclusion, noting it’s a conservative issue that deals with both constitutional and states' rights.

For the Marijuana Policy Project, he hopes to encourage Congress to change the law on a federal ban and allow states to decide their own policies. Currently, 11 states have laws allowing sick patients access to marijuana, but those patients can still be arrested under federal rules.

"(Government) has become significantly more invasive since 9/11, and government power over the medical use of marijuana is one of those areas" where federal authority over the states is being questioned by "a lot of conservatives and liberals alike," he said in explaining how he arrived at MPP.

"Reforming marijuana is not just a liberal issue, it's a small government issue," said Dan Bernath, spokesman for MPP. "There are already a lot of conservatives who see this as a conservative issue."

No Fan of Bush

Barr helped craft the sweeping anti-terror, law enforcement legislation, also known as the Patriot Act, in the wake of the Sept. 11, 2001, terrror attacks. He insists he had questions then regarding the more controversial measures involving relaxed warrants, data sharing and surveillance, but went along after pushing for sunset provisions that would require Congress to take a second look down the road.

By the time that second look came along last year, Barr had joined the ACLU, as well as a host of conservative groups in calling for more checks and balances in the current language and fighting against additional powers advocated by the Bush administration and the Republican leadership in Congress.

"We are more effective, both of us — the ACLU and Bob Barr and the conservative groups — when we show there are issues around which we can unite without overt partisanship," said ACLU legislative director Caroline Frederickson, who added that Barr had been a "natural ally" during his tenure in office.

The two certainly share common gripes with the Bush administration. Barr has blasted what he calls an encroaching police state where law-abiding citizens are treated as criminals in the name of homeland security, and personal data is swapped and mined by federal agencies and their private partners. He has zeroed in on Bush's warrantless domestic spy program at the National Security Agency, calling it unconstitutional.

When the Department of Defense announced in 2005 that it would be expanding its scope to domestic homeland security operations, including surveillance, Barr was incensed.

"Do we want, as a free people, with the notion of privacy enshrined in the Constitution and based on the very clear limits and defined role of government, to be in a society where not just the police, but the military are on the street corners gathering intelligence on citizens, sharing that data, manipulating that data?" he asked at the time.

Barr's evolution has led many members of the conservative circles in Georgia "scratching their heads" over his newfound zeal, said Todd Young, who worked closely with Barr at the conservative Southeastern Legal Foundation in Atlanta until Barr left in 2005

Young said many are concluding, "Wait a second, there are ways to do what you want to do without associating yourself with the ACLU."

Young acknowledges that Barr is not alone in his perspective and his recent notoreity has as much to do with his convictions as with the desire of conservatives to find new alternatives.

"Interestingly enough, he may have tapped into a vein of thought here. The last election found a lot of dissatisfaction with the Republican majority in Congress," Young said, noting that while the foundation's association with Barr ended amicably, the group just doesn’t agree with him on much these days.

"I think (Barr) is finding his political home, something that fits his issue-base right now and more power to him," said Young, who called Barr "very courageous."

Conservatives and the Drug War

Ironically, the Libertarians had funded Barr's primary opponent, now Rep. John Linder, in 2002, because of Barr's anti-drug stance. Barr lost to Linder and left Congress.

"If we can at least bump out Barr we can send a message," Libertarian Party spokesman George Getz said at the time.

Barr suggested his focus at MPP today is concerned only with defending state medical marijuana laws. He would not say whether he has had changed his mind about the criminalization of marijuana and the drug war.

But Roger Pilon, legal studies director at the Cato Institute, said he believes that Barr is moving toward a political position inhabited by many libertarian conservatives. And he welcomes him.

"I am absolutely thrilled with this change of heart because it gives me hope that others can see the light and see the errors of this modern prohibition" also known as the unsuccessful war on drugs, Pilon said.

"Each of us, at any point in our lives, is a work in progress, we come to see things later in life that we grasped only dimly early on," he added.

Barr's supporters point out that true conservatives, like Barr, have always railed against encroaching federal powers and government abuse of authority.

A man faithful to the Constitution doesn't stop criticizing presidents when the letter after their names change, Barr explained.

"I don’t think any president — Democrat or Republican — should be allowed to play games with the laws of this country whether its obstruction of justice or perjury to laws this president seems to have violated under the circumstances of electronic surveillance without a court order, spying on citizens of the United States," he said.