On November 4, 2010, the Federal Labor Relations Authority rejected the argument that unionization of TSA employees would pose a threat to national security and adopted the position of the AFL-CIO in order to allow passenger screeners, baggage screeners, and lead screeners, of the TSA to be represented by a union for the purpose of collective bargaining.
The full text of the decision can be found here.
An interesting article on this issue: Mark Roth & Jamison Grella, First Line Defenders as Second Class Citizens: Collective Bargaining Rights for TSA Employees and National Security Make Good Bedfellows, 1 Am. Nat’l Security L. Brief 117 (2010). Which will be available soon at www.nationalsecuritylawbrief.com.