Since joining the Libertarian Party, Barr has reversed his previous stance favoring the War on Drugs and is now a lobbyist for the Marijuana Policy Project.
Since leaving Congress in 2003, Barr has become a vocal opponent of the Patriot Act and has stated that he regrets voting for it, claiming that the Bush Administration has used it to further erode due process even in nonterrorism matters. He claims that the Clinton administration did much of the same thing.[11] In 2005--the year the Patriot Act was due for renewal he helped found an organization called Patriots to Restore Checks and Balances, a bipartisan group dedicated to eliminating aspects of the Patriot Act that could potentially affect law-abiding citizens rather than terrorists, and to "restore traditional checks and balances on government power so the country can effectively fight terror without sacrificing the rights of innocent Americans, rights that are guaranteed by the Constitution."[14] Barr still serves as the group's chairman.