22 U.S. Code § 4118 - Administrative provisions
If the Department has received from any individual a written assignment which authorizes the Department to deduct from the salary of that individual amounts for the payment of regular and periodic dues of the exclusive representative, the Department shall honor the assignment. Any such assignment shall be made at no cost to the exclusive representative or the individual. Except as provided in subsection (b), any such assignment may not be revoked for a period of one year from its execution.
During any period when no labor organization is certified as the exclusive representative of employees in the Department, the Department shall have the duty to negotiate with a labor organization which has filed a petition under section 4111(b)(1)(A) of this title alleging that 10 percent of the employees in the Department have membership in the organization if the Board has determined that the petition is valid. Negotiations under this subsection shall be concerned solely with the deduction of dues of the labor organization from the salary of the individuals who are members of the labor organization and who make a voluntary allotment for that purpose. Any agreement between the Department and a labor organization under this subsection shall terminate upon the certification of an exclusive representative of any employees to whom the agreement applies.