During the early rounds of hearings on the proposed Homeland Security department, which eventually could absorb some 170,000 federal employees now working more than a dozen agencies or subagencies, civil service leaders in Congress have voiced opposition to the administration’s plan to give the agency greater freedoms over personnel policy, including over employee union rights. They have been telling administration officials that federal agencies already have substantial flexibility in personnel policies and said employees’ rights should not be taken away in the name of national security.