The New York Daily News first reported the dismissal, which took place Aug. 28.
Clemens' attorney, Rusty Hardin, filed the suit on Jan. 6, 2008, in Houston, claiming McNamee was "malicious and grossly negligent" in his remarks about Clemens to baseball investigator George Mitchell and SI.com.
Federal judge Keith Ellison of the U.S. District Court dismissed the case with prejudice, meaning Clemens cannot file the suit again. Clemens does, however, retain the right to appeal.
"Brian has defeated Clemens in Texas," McNamee's lawyer, Richard Emery of the Manhattan firm of Celli, Emery, Brinckerhoff & Abady, told the Daily News. "And now the battleground moves to New York."
Clemens is under investigation by a federal grand jury in Washington that is trying to determine whether he lied when he told a congressional committee in February 2008 that he had not used steroids.
McNamee has told federal agents, Mitchell and a House committee that he injected Clemens more than a dozen times with steroids and human growth hormone from 1998 to 2001. Clemens has denied using performance-enhancing drugs.
Ellison previously had dismissed much of Clemens' lawsuit in February 2009, saying the Southern District in Houston did not have jurisdiction, and McNamee's conversations with Mitchell were protected by his immunity deal with the government.
In late June, Clemens' legal team sought to revive some of the claims in the defamation suit against McNamee, but Ellison affirmed his February ruling.
In late July, McNamee sued Clemens in federal court in Brooklyn, alleging the pitcher "waged a defamatory public relations campaign against McNamee ... intended to deceive the public and Congress into falsely believing that McNamee is a liar."
The lawsuit quotes Clemens saying in a YouTube video in 2007 that McNamee "did not inject steroids into my body either when I played in Toronto for the Blue Jays or the New York Yankees."
It also cites an interview with ESPN in May in which Clemens, when asked about McNamee, responded that it was a case of "somebody out there that is really crawling up your back to make a buck."
The suit, which seeks unspecified damages, claims Clemens' statements have "humiliated McNamee, destroyed his reputation, both personally and professionally, and caused him severe emotional distress."
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