The Virginia Labor Law Library: 
Executive Order 13201

In Communication Workers v. Beck, 487 U.S. 735 (1988) (link courtesy FindLaw), the Supreme Court ruled that workers who are represented by unions and pay agency fees instead of union dues cannot be required to contribute to union expenditures not related to collective bargaining, contract administration, or grievance administration.

On February 17, 2001, the U.S. Department of Labor issued Executive Order 13201, which requires federal contractors and subcontractors to post a notice advising employees represented by unions of their rights under Beck.  It also requires them to include a clause in their related subcontracts and purchase orders requiring that the subcontractors and vendors post the notice. It became effective 60 days after its issuance.

On April 18, 2001, the DOL issued an Interim Procedural Notice (Federal Register: May 16, 2001, Volume 66, Number 95, Page 27416-27417), to provide federal contractors and subcontractors with guidance for compliance with E.O. 13201.