The Statute: § 7115. Allotments to representatives
(a) If an agency has received from an employee in an appropriate unit a written assignment which authorizes the agency to deduct from the pay of the employee amounts for the payment of regular and periodic dues of the exclusive representative of the unit, the agency shall honor the assignment and make an appropriate allotment pursuant to the assignment. Any such allotment shall be made at no cost to the exclusive representative or the employee. Except as provided under subsection (b) of this section, any such assignment may not be revoked for a period of 1 year.
(b) An allotment under subsection (a) of this section for the deduction of dues with respect to any employee shall terminate when--
(1) the agreement between the agency and the exclusive representative involved ceases to be applicable to the employee; or
(2) the employee is suspended or expelled from membership in the exclusive representative.
(c)(1) Subject to paragraph (2)