They can prove that he broke the Intelligence Identities Protection Act of 1982.
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SEC. 601. <50 U.S.C. 421> (a) Whoever, having or having had authorized access to classified information that identifies a covert agent, intentionally discloses any information identifying such covert agent to any individual not authorized to receive classified information, knowing that the information disclosed so identifies such covert agent and that the United States is taking affirmative measures to conceal such covert agent’s intelligence relationship to the United States, shall be fined under title 18, United States Code, or imprisoned not more than ten years, or both.
(b) Whoever, as a result of having authorized access to classified information, learns the identity of a covert agent and intentionally discloses any information identifying such covert agent to any individual not authorized to receive classified information, knowing that the information disclosed so identifies such covert agent and that the United States is taking affirmative measures to conceal such covert agent’s intelligence relationship to the United States, shall be fined under title 18, United States Code, or imprisoned not more than five years, or both.
(c) Whoever, in the course of a pattern of activities intended to identify and expose covert agents and with reason to believe that such activities would impair or impede the foreign intelligence activities of the United States, discloses any information that identifies an individual as a covert agent to any individual not authorized to receive classified information, knowing that the information disclosed so identifies such individual and that the United States is taking affirmative measures to conceal such individual’s classified intelligence relationship to the United States, shall be fined under title 18, United States Code, or imprisoned not more than three years, or both.
(d) A term of imprisonment imposed under this section shall be consecutive to any other sentence of imprisonment.
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http://www.fas.org/irp/offdocs/laws/iipa.html >
Rove won't be convicted of treason, but maybe he'll get nailed on this...?