Limitations placed on the movement of labor are seen as major impediments to the growth both of trade in services and of the economy overall. The temporary movement of service providers is generally expected to be less politically sensitive than the permanent movement of labor. Therefore, it remains a puzzle why the UK, a major proponent of multilateral trade liberalization in services, made a slightly below-the-EU-average offer on the free movement of natural persons (Market Access Mode 4) as part of the first EU offer in the WTO Doha Round in February 2003, but then in 2004 chose not to limit the free movement of labor from the new Member States of the EU as most other "old” Member States did. The main argument is that the policy choices reflect the aim of the UKgovernment to retain flexibility in and external sovereign control over labor immigration policies. This allows it to maintain flexible labor markets within the UK and the extended EU Internal Market, while at the same time obtaining the support for these policies from the two domestic societal actors—the trade unions and the employers—each for its own self-interested reasons. The study contributes to the literature on immigration control policies and trade in services.