EU liberalization has a tendency to occur even in the most disputed policy areas. Drawing on two approaches, gradual institutional theories and differentiated integration, this contribution seeks to clarify how the EU achieved liberalization policy in the postal market. A qualitative study of the decision-making process of the Postal Directive suggests that differential growth, in particular related to time rules in existing legislation that ensure future re-negotiations and concessions that constrain resistance, have contributed to policy change in EU postal services. This occurred under the conditions of instability in the market due to an unclear line between who is allowed to compete where, social norms that made it politically costly to create barriers to further integration and longevity that created desires to put an end to a process
