http://www.patentofficelawsuit.info/irs_6103.htm
§ Section 6103. - Confidentiality and disclosure of returns and return information
(a) General rule
Returns and return information shall be confidential, and except as authorized by this title -
(1) no officer or employee of the United States, ... shall disclose any return or return information obtained by him in any manner in connection with his service as such an officer or an employee or otherwise or under the provisions of this section. For purposes of this subsection, the term ‘’officer or employee’’ includes a former officer or employee.