Permissibility of the Administration and Use of the Federal Payroll Allocation System by Executive Branch Employees for Contributions to Political Action Committees: Memorandum for the Director, Office of Personnel Management [February 22, 1995] [open pdf - 144KB]
"Early last year, the Office of Personnel Management ('OPM') advised executive branch officials that executive branch employees now are permitted to make voluntary salary allotments to political action committees ('PACs'), using the mechanisms otherwise available to federal employees for salary allotments to other organizations and institutions. Under the salary-allotment system, a federal employee can authorize federal payroll administrators to transmit portions of his or her salary, on a regular basis, to certain persons or institutions designated by the assigning employee. […] While we have concluded that use of the salary-allocation system for PAC contributions would be lawful under certain circumstances, nevertheless the head of each federal agency has the discretion to decide whether to make the system available for that purpose to employees of the agency."
United States. Department of Justice: http://www.justice.gov/